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Microbiology BOC
Microbiology BOC
400
Microbiology
Undergraduate 4
11/26/2011

Additional Microbiology Flashcards

 


 

Cards

Term

Preanalytical and susceptibility Testing

 

Proper media for culture of a urethral drainage from a man include:

Definition
Chocolate and modified Thayer Martin agars
Term

A sheep blood agar plate inoculated with 0.001 mL of urine grows 70 colonies of Staphylococcus aureus. How many colony forming units per mL of urine should be reported? 

 

Definition
70,000
Term
The lowest concentration of antibiotic that inhibits growth of a test organism is the: 
Definition
minimum inhibitory concentration.
Term
Which of the following clean catch urine culture colony counts indicates the patient likely has a urinary tract infection?
Definition
10 CFU/mL
Term

 

the steam autoclave method of sterilization:

Definition
uses 15 lbs of pressure for 15 mins
Term
The expected colony count in a suprapubic urine from a healthy individual is:
Definition
0 CFU/mL
Term
An aspirate of a deep wound was plated on blood agar plates and incubated aerobically and anaerobically. At 24 hours there was growth on both plates. This indicates that the organism is a:
Definition
facultative anaerobe
Term
The proper blood to broth ratio for blood cultures to reduce the antibacterial effect of serum in adults is: 
Definition
1:10
Term
A penicillin-resistant Neisseria gonorrhoeae produces:
Definition
beta-lactamase
Term
Which selective medium is used for the isolation of gram positive microorganisms?
Definition
Columbia CNA with 5% sheep blood
Term
The most sensitive substrate for the detection of beta-lactamases is:
Definition

nitrocefin

The chromogenic cephalosporin test using nitorcefin is the most sensitive and specific test for the detection of beta lactamase.

Term

A Staphylococcus aureus isolate has an MIC of 4 ug/mL to oxicillin.There is uncertainty as to whether this represents an oxacillin (heteroresistant) resistant strain or a hyperproducer of beta-lactamase.

Strain           Oxacillin          Amoxicillin-clavulanic acid 

strain A         susceptible       susceptible

strain B          susceptible       resistant

strain C          resistant            susceptible

strain D           resistant            resistant\

Based on the above results for oxacillin and amoxicillin-clavulanic acid, which is heteroresistant 

Definition
Strain D
Term
An enterococcus isoloted from multiple blood cultures in a patient with endocarditis should be:
Definition
screened for high level aminoglycoside resistance
Term
In the Kirby-Bauer disc diffusion susceptibility test, which variable is critical when testing Pseudomonas species for antibiotic sustibility to amosides?
Definition

cation content of the media

(Ph)

Term
The procedure that assures the most accurate detection of mec-a mediated oxacillin resistance in routine broth microdilution susceptibility testing  against S. aureus is:
Definition
use of cefoxitin for testing
Term
Three sets of blood cultures were obtained from an adult patient with fever and suspected endocarditus. The aerobic bottle of one set had growth of staphylococcus epidermidis at 5 days of incubation. This indicates that:
Definition
The organism is most likely a contaminant
Term
Susceptibility testing performed on quality control organisms using a new media lot number yielded zone sizes that were too large for all antobiotics tested. The testing was repeted using media from a previously used lot number, and all zone sizes were acceptible. Which of the following best explaines the unacceptable zone sizes?
Definition
The depth of the media was too thin
Term

When performing a stool culture, a colony type typical of an enteric pathogen is subcultured on a blood agar plate. The resulting pure culture is screened with several test to obtain the following resilts:

TSI:    acid butt, alkaline slant, nogas, no H2S

phenylaninine deaminase: negative

motility: positive

serology typing: (shigella subgroup B)

 The serological typing is verified with new kit and controls. The best course of action would be to:

Definition
Verify reactivity of motility medium with positive and negative controls.
Term
In order to isolate Camoylobacter coli/jejuni the fecal specimen should be:
Definition

inoculated onto selective plating media and incubated in reduced oxygen with added CO2 at 42*C

(micraerophillic atmosphere and selective media are needed for Campylobacter)

Term

An expectorated sputum is sent to the laboratory for culture from a patient with respiratory distress. The gram stain of the specimen shows many squamous epithelial cells (>/lpf) and rare neutrophlis. The microscope appearance of the organisms present include:

moderate gram positive cocci in chains and diplococci

moderate gram-negative diplococci

moderate palisading gram-positive bacilli

This Gram stain is most indicative of :

 

Definition
oropharyangeal flora
Term
Which type of microscope would be most useful in examining viruses and the structure of microbial cells?
Definition
electron
Term
After satisfactory performance of daily disk diffusion susceptibility quality control is documented, the frequency of quality control can be reduced to: 
Definition
every week
Term
In disc diffusion susceptibility testing, as antimicrobial agent diffuses away from the disk, the concentration of antibiotic is:
Definition
decreased
Term
The most common cause for failure of a GasPac anaerobic jar to establlish an adequate enviroment for anaerobic incubation is:
Definition
catalyst that have become inactivated after repeated use
Term
Which of the following is the most appropriate method for collecting a urine specimen from a patient with an indwelling catherter?
Definition
aspirate urine aseptically from the catheter tubing.
Term
Which of the following specimen request is acceptable?
Definition
urine for culture of acid fast bacilli
Term
Which of the following groups of specimens would be acceptable for anaerobic culture?
Definition
pleural fluid, brain abcess.
Term
A liquid fecal specimen from a three month old infant is submitted for microbiological examination. In addition to culture on routine media for Salmonella and Shigella, this specimen should be routinely:
Definition
examined for the presence of Campylobacter sp
Term
Cerebrospinal fluid from a febrile 25 year old man with possible meningitus is rushed to the laboratory for a stat Gram stain and culture.While performing the Gram stain, the technologist accidently spills most of the specimen. The smear shows many neutrophils and no microorganisms. Since there is only enough CSF to inoculate one plate, the technologist should usa a:
Definition
chocolate agar plate
Term

A diabetic foot swab from a 82 year old woman with recurrent infections is submitted for culture. The Gram stain reveals:

many neutrophils, no squamous epithelial cells

many gram negative bacilli

many gram positive cocci in chains

The physican request that all pathogens be worked up. In addition to the sheep blood and MacConkey agar plates routinely used for wound cultures, the technologist might also process:

 

Definition
a CNA agar plate
Term
Which of the following is the most appropriate specimen source and primary media battery?
Definition
endocervical- chocolate, Martin Lewis
Term
Which of the following is the most appropriate organism and media combination?
Definition
Yersinia enterocolitica- cefsulodin-irgasan-novibiocin (CIN)
Term

A Gram stain from a swab of a hand wound reveals:

moderate neutrophils

no squamous epithelial cells

moderate gram positive cocci in chains

moderate large gram negative bacilli

Select the appropriate media that will selectively isolate each organism.

 

Definition
Columbia CNA, MacConkey
Term
Upon review of a sputum Gram stain, The technician notes that the nuclei of all of the neutrophils present in the smear are staining dark blue. The best explanation for this finding is:
Definition
the slide was inadequately decolorized with acetone/alcohol
Term
When performing a Kovac indole test, the substrate must contain:
Definition

tryptophan

 

The indole test is used for detrmining an organisms ability to produce indole from deamination of tryptophan.

Term
The ONPG test allows organisms to be classified as a lactose fermenter by testing for which of the following?
Definition

beta-galactosidase

Through the action of the enzyme beta-galactosidase , ONPG cleaves into galactose and o-nitrophenol (a yellow compound)

Term
Sodium bicarbonate and sodium citrate are componets of which of the following?
Definition

JEMBEC system

The JEMBEC system is a transport and inoculation medium used for direct plating of specimens for N. gonorrhoeae. Chocolate- based selective medium is inoculated with the specimen. This is placed in an impermeable plastic bag with a bi-carbonate sodium citrate pellet that absorbs moisture to generate a carbon dioxide-rich envoroment.

Term

Chocolate agar base containing vancoumycin,

 colistin, anisomycin, and trimethoprim is also known as:

Definition
Martin Lewis agar
Term
A medium that aids in the presumptive identification of organisms based on their appearance on the medium is called:
Definition
differential
Term
SPS is used as an anticoagulant for blood cultures because it:
Definition
inactivates neutrophils and components of serum complement:
Term
When evluating a new susceptibility testing system, if the new system characterizes a susceptible isolate as resistant , this is termed a:
Definition
major error
Term
Which of the following methods is inadequate for the detection of vancoumycin-intermediate S. aureus?
Definition

disk diffusion.

The disk diffusion procedure will not differentiate S. aureus strains with reduced susceptibility to vancoumycin (MICs 4-8) from susceptible strains even when incubated for 24 hours.

Term
In the disk diffusion susceptibility test, which of the following can result if disks are placed on the inoculated media and left at room temperature for an hour before incubation?
Definition

zones of larger diameter would result

 

a delay of more than 15 mins between placing the disks on the inoculated plate and incubation permits excess prediffusion of the antimicrobial agent  from the disk. This would result in a larger than expected zone diameter.

Term
Which of the follwing factors would make an organism appear to be more resistant on a disk diffusion sustibility test?
Definition
too many organisms in the innoculum
Term
First generation cephalosporins can be adequately repersented by:
Definition

cephalothin

cefotetin and cefoxitin are second generation and ceftriaxone is a third generation.

Term
An antibiotic that inhibits cell wall synthesis is:
Definition
penicillin
Term
Which one of the following organisms does not require susceptibility testing to the antimicrobial indicated when isolated from a clinically significant source.
Definition

Streptococcus pyogenes-penicillin

 

susceptibility testing should be performed when susceptibility of the organism cannot be reliably perdicted and resistance is known or suspected. Susceptibilityntesting of penicillin for treatment of S pyogenes does not need to be performed routinely since resistance has not been documented.

Term
Which of the following antibiotics would routinely be tested and reported for isolates of Pseudomonas aruginosa?
Definition

Gentamycin

(Gentamycin is an aminoglycoside)

Term
Which of the folllowing must be incubated in a microaerophilic enviroment for optimal recovery of the organism?
Definition
Campylobacter jejuni
Term
Diagnosis of typhoid fever can be confirmed best by culture of :
Definition

blood

 

The sensitivity of blood culture is 50-70%. Stool cultures are positive in < 50% of patients and urine cultures are positive even less frequently. Bone marrow has a sensitivity of up to 90%.

Term
Vibrio parahemolyticus can be isolated best from feces on:
Definition
thiosulfate citrate bile salts (TCBS) agar
Term
Which of the following media can be used to culture Campylobacter jejuni?
Definition
Skirrow medium
Term
Test for beta-lactamase in Heaemophilus influenza:
Definition
should be performed on all blood and CSF isolates
Term
Media used to support growth of Legionella pneumophilia should contain which of the following additives?
Definition
charcoal and yeast extract
Term
The best medium for culture of Bordetella pertusis is:
Definition
Regan Lowe agar
Term
The best medium for Francesella tularensis is:
Definition
Cystine glucose blood agar
Term
The most rapid method for detection of Francesella tularensis is:
Definition
fluorescent antibody staining techniques on clinical specimens
Term
When processing throat swabs for group A Streptococcus culture, the medium of choice is:
Definition
sheep blood agar
Term
The ability to detect oxacillin-resistant Staphylococcus aureus may be enhanced by:
Definition
using Mueller-Hinton broth with 2% NaCl
Term
The optimal wound specimen for culture of anaerobic organisms should be:
Definition
a syringe filled with pus; obtained before administration of antibiotics
Term
A 21 year old patient presents with pharyngitis. A throat swab is collected and submitted for anaerobic culture. This specimen should be:
Definition

rejected as unacceptible

ananerobic bacteria do not cause pharyngitis

Term
Anaerobic sustibility testing is helpful in the management of patients with:
Definition
synovial infections
Term
An antibiotic used to supress or kill contaminating fungi in media is:
Definition
cyclohexamide
Term
Production of beta-lactamase is inducible in which of the following:
Definition

Staphylococcus aureus

Some bacteria such as Enterococcus sp, H. influenza and Neisseria gonorrhoeae continualy produce beta lactamase. S.aureus produces beta-lactamase only after exposure to an inducing agent (such as penicillin) C diptheriae and S. pyogenes do not produce beta lactamase. 

Term

[image]

A sputum specimen is recieved for culture and Gram stain. The Gram stain smear from this specimen seen in the image

The technologist best course of action would be to:

Definition

Call the patient care area and request a new specimen.

here are several sputum screening systems for acessesing the quality of respiratory specimens. In general, neutrophils are a positive indicator of quality, and squamous epithelial cells are a negative indicator of quality, suggesting oropharyngeal contamination. This specimen contains an abundance of squamous cells, (>10/low power field), and would be unaccepitable for cultue.

Term
A technologist is reading a Gram stain from a CSF and observes many neutrophils and lancet shaped gram-positive diplococci. Which set of chemistry and hemotology CSF results would most likely be seen in someone with this type of infection?
Definition
WBC increased, glucose decreased, Protein increased
Term

Refer to the following:

                                   64    32    16        8         4          2     Control g/mL

                     

gentamycin     Ο   Ο   Ο    Ο    Ο     Ο     positive

 

Examine the broth microdilution susceptibility test shown above and determine the MIC for Gentamycin.

Definition
< 2 ug/mL
Term
Which of the following test is used to monitor bactericidal activity during antimicrobic therapy in cases of endocarditis?
Definition

Schlicter

the serum bactericidal or Schlicter test can be used to acess the activity of patients serum when they are recieving long term therapy for endocarditis or osteomyelitis. High titers of anti bacterial activity in the serum suggest adequate dosing, a nontolerant isolate or normal elimination of the antibiotic.

Term

Quality control results for disk diffusion susceptibility test yield the following results:

aminoglycoside zones too small and penicillin zones too large. This is most likely due to the:

Definition
Ph of the Mueller-Hinton agar being too low
Term
When using a control strain of staphylococcus aureus, the technologist notices that the zone around the oxacillin disk is too small. Which of the following is the most likely explanation?
Definition
use of outdated oxacillin disks
Term
In the disk diffusion method of determining antibiotic susceptibility, the size of the inhibition zone used to indicate susceptibility has been determined by:
Definition
correlating the zone size with minimum inhibitory concentrations
Term
Which of the following organisms may be mistaken for Neissseria gonorrhoeae in Gram stained smears of uterine cervex exudates:
Definition
Moraxella osloensis
Term
A 73 year old man diagnosed as having pneumococcal meningitis is not responding to his penicillin therapy. Which of the following test should be performed on the isolate to best determine this organisms susceptibility to penicillin?
Definition

oxacillin disk diffusion

With the exception of the oxacillin disk screening test, disk diffusion is not recommended for testing S.pneumoniae aginst beta-lactam agents. S.pneumoniae does not produce beta-lactamase, so beta-latamase testing would not be useful

Term
Salmonella enteritidis is isolated from multiple blood cultures in a patient with fever. Susceptible results are as follows: ampicillin-susceptible, ceftriaxone- susceptible, ciprofloxacin-susceptible, trimethoprim/sulfamethoxazole-resistant. What is the next best step?
Definition
Test the isolate aginst nalidixic acid and if resistant report the ciprofloxacin as resistant.
Term
Which of the following antimicrobials would be inappropriate to report on an E coli isolated from a wound culture
Definition

nitrofurantoin

certian antimicrobials, such as nitrofurantoin and norfloxacin, are used only or primairly to treat urinay tract infections. These agents should not be reported for pathogens recovered from other sites of infections.

Term

The susceptibility results below are reported on an Enterococcus faecalis isolated from peritoneal fluid:

Ampicillin:     susceptible

vancoumycin: resistant

clindamycin;  susceptible

levofloxacin:   resistant

linezolid:  susceptible

The physican calls questioning the results. Which of the following should have been done before the report was called:   

Definition
The clindamycin result should have been removed from the report since it is inactive aginst enterococcus.
Term

A D test is performed on an isolate of Staphylococcus aureus to determine inducible clindamycin resistance:

[image]

Definition
erythromycin resistant; clindamycin susceptible
Term
Which of the following combinations is useful for confirming the presence of extended  spectrum beta-lactamase in E-coli?
Definition
ceftazidime + clavulanic acid
Term
Enyzmatic drug modification is a mechanism of resistance for which antimicrobial
Definition
gentamycin
Term
Which of the following is the most important variable in the recovery of organisms in patients with bacteremia?
Definition
The volume of the blood cultured.
Term
A 24 year old man presents with pain on urination and urethral discharge. A gram stain of the discharge is seen in the image:[image]
Definition
Neisseria gonorrhoae
Term

[image]A 10 year old child with cystic fibrosis persents with cough and shortness of breath. er sputum Gram stain is seen in this image:

Based on the gram stain what would be the best medium and incubation condition to optimze recovery of the organism seen?

 

Definition
Chocolate agar incubated in CO2
Term

[image]

The image depicts a Gram stain of a knee fluid from a patient who has recently undergone knee replacement surgery:

 

Definition
Gram positive cocci suggestive of streptococcus
Term
A vaginal/rectal swab is collected from a pregnant patient to screen for group B streptococcus colonization. What is the best medium to use for the specimen inoculation?
Definition
LIM broth
Term
A pregnant patient is screened at 36 weeks gestation for group B streptococccus (GBS). A vaginal swab is collected and cultured in Todd-Hewitt broth with 8 ug bentamicin /mL and 15 ug nalidixic acid/mL. The broth is subcultured onto sheep blood agar after 24 hours incubation. No GBS are seen on the subculture and the results are negative. The patient later goes on to deliver an infant wiith early onset GBS disease. What is the most likely reason for the negative GBS culture?
Definition
A vaginal swab was collected instead of a vaginal/rectal swab
Term

Susceptibility testing is performed on a Staphylococcus aureus isolate from a blood culture with the following results:

oxacillin:     resistant

cefazolin:    susceptible

Clindamycin:  susceptible

erythromycin: susceptible

trimethoprim/sulfamethoxazole: susceptible

vancoumycin: susceptible

What should the technologist do: 

Definition

the cefazolin result should be changed to resistant since the oxacillin result is resistant

Oxicillin resistant staphylococci are resistant to all beta lactam agents, beta lactam/beta lactamase inhibitor commbinatons and carbapenams. results for these antibiotics should be reorted as resistant or should not be reported

Term
To quality control the autoclave, a vial of bacillus stearothermophilus is autoclaved and should then be:
Definition
incubated at 56*
Term
In a quality control procedure on a new batch of Mueller-Hinton plates using a stock culture of Staphylococcus areus, all the disk zone sizes are too small. The most likely reason for this is that the:
Definition
bacterial suspension was not diluted to the proper concentration.
Term
Which of the following combinations of organisms would be appropriate as controls to test the functions listed?
Definition
indole -negative Escherichia coli and proteus mirabilis
Term
A urine gram stain shows gram positive cocci in clusters. The organism tested catalase positive. To speciate this organism from culture, the technician should perform a coagulase test and a:
Definition
novobiocin susceptibility
Term
The gram stain from a blood culture shows gram positive cocci in chains, No growth occurs on blood agar plates incubated both aerobically and anaerobically. Additional testing should be done to detect the presence of:
Definition

Abiotrophia defectica

Nutritionally deficient streptococcus such as Abiotrophia defectica do not grow on sheep blood agar without the addition of cysteine or proximity to S. aureus

Term
Viridans streptococci can be differentiated from streptococcus pneumoniae by:
Definition
bile soluability
Term
A reliable test for distinguishing Staphylococcus areues from other staphylococcus is:
Definition
coagulase
Term
The optochin (ethylhydrocupreine hydrochloride) disk is used for the identificaton of:
Definition

Streptococcus pneumoniae

optochin susceptibility is used to differentiat S. pneumoniae, which are susceptible , from other  alpha hemolytic streptococci which are resistant

Term
In the optochin susceptibility test, if there is a zone of inhibition of 19-30 mm surrounding the disk following an overnight incubation ay 37*C , the colony most likely consist of :
Definition

pneumococcus

(Strep pneumococcus is susceptible, other alpha hemolytic strep are resistant)

Term
Which 2 diseases are usually preceded by infection with beta hemoltic streptococci?
Definition
glomerulonephritis, rheumatic fever.
Term
The enterotoxin produced by certian strains of hemolytic, coagulase positive Staphylococcus aureus :
Definition
causes one type of bacterial food poisioning
Term
A gamma hemolytic Streptococcus that blackens bile esculin agar but does not grow in 6.5% NaCl broth is most likely:
Definition
group D Streptococcus
Term
Gram stain examination from a blood culture bottle shows dark blue, spherical organisms in clusters. Growth on sheep blood agar shows small, round, pale yellow colonies. Further test should include:
Definition
catalase production and coagulase test
Term
Gram positive cocci in chains are seen on a gram stain from a blood culture. The organism grows as a beta hemolytic colony. Further test that could be performed include:
Definition

bile esculin, PYR, bacitracin, and hippurate

 

bile esculin, PYR, bacitracin and hippurate are biochemical test used in the presumptive or definitive identification of beta-hemolytic streptococci such as S. pyogenes, S agalactiae and Enterococcus

Term
Nutritionally deficient streptocci are:
Definition
in the genera Granulicatella and Abiotrophia
Term

After 21 hours a blood culture from a newborn grows catalase-negative, gram positive cocci, The bacterial colonies are small, translucient and beta-hemolytic on a blood agar plate. Biochemical test results of a pure culture are:

Bacitracin:  resistant

CAMP reaction   positive

bile esculin:  not hydrolyzed

6.5% NaCl:  no growth

Assuming that all controls react properly and reactions are verified , the next step would be to:

Definition

preform a streptococcus group typing.

this describes Strep agalactiae. This can be confirmed by streptococcus antigen typing.

Term
A beta hemolytic streptococcus that has been isolated from an ear culture grows up to the edge of a 0.04 unit bacitracin disk. Which of the following test would help to determine if the organism is enterococcus.
Definition

growth in 6.5% NCl broth.

 

Enterococcus has the ability to grow in the presence of high salt concentrations such as  6.5% NaCl broth

Term
The organism most commonly associated with neonatal purulent meningitis is:
Definition
 group B streptococccus
Term
An important cause of acute exudative pharyngitus is:
Definition
Streptococcus pyogenes
Term
Of the following bacteria, the most frequent cause of prosthetic heart valve infections occuring within 2-3 months after surgery is:
Definition
streptococcus epidermidis
Term
Which of the 2 different antimicrobial agents listed below are commonly used and may result in synergistic action in the treatment of endocarditis caused by Enterococcus faecalis
Definition
a penicillin derivative and an aminoglycoside
Term
A catherized urine is inoculated onto blood and MacConkey agar using a 0.01 mL loopi. after 48 hours, 68 colonies of a small translucent nonhemolytic organism grew on blood agar but not MacConkey. Testing reveals small gram-positive, catalase negative cocci. The perliminary report and follow up testing would be:
Definition
growth of 6,800 colonies/mL of a streptococcus species, esculin hydrolysis and NaCl growth test to follow
Term
Children who have infections with Beta -hemolytic streptococci can develop:
Definition
acute glomerulonephritis
Term

A Gram positive coccus isolated from a blood culture has the following characteristics:

optochin susceptibility:                     negative

bacitracin 0.04 units suscepibility:   negative

bile esculin hydrolysis                      negative

hippurate hydrolysis:                        positive

catalase:                                            negative 

The organism is most likely:

 

Definition

Streptococcus agalactiae

Streptococcus agalactiae is catalase and bile esculin hydrolysis negetive and bacitracin and optochin resistant and hydrolyses hippurate

Term
A beta-hemolytic Streptococcus that is bacitracin resistant and camp positive is
Definition
group B strep
Term
Group B, beta-hemolytic streptococci may be distinguished from other hemolytic streptococci by which of the following procedures?
Definition
latex antigen typing
Term
It is important to differentiate between Enterococcus and group D streptococcus because:
Definition
Enterococcus often show more antibiotic resistance than group D streptococcus
Term
Streptococcus pneumoniae can be differentiated beat from the viridans group by
Definition
bile solubility
Term
Characteristically enterococci are:
Definition
relatively resistant to penicillin
Term
A beta hemolytic, catalase positive, gram positive coccus is coagulase negative by the slide coagulase test. Which of the following is the most appropriate action in identification of this organism?
Definition
do a tube coagulase test to confirm the slide test
Term
Which of the following would best differentiate Streptococcus agalactiae fromStreptococcus pyogenes?
Definition
hydrolysis of sodium hippurate
Term
The most critical distinction between Staphylococcus aureus and other Staphylococcus is:
Definition
coagulase production
Term
Which of the folllowing organisms to date is considered universally susceptible to pencillin?
Definition
Streptococcus pyogenes
Term
A beta hemolytic gram=positive coccus was isolated from the cerebrospinal fluid of a two day old infant with signs of meningitis. The isolate grew on sheep blood agar under aerobic conditions and was resistant to a bacitracin disc Which of the following should be performed for the identification of the organism?.
Definition

latex antigen typing

The most likley organism is Streptococcus agalactiae. Polysacchride  antigen typing will confirm the identificaton the identification of S. agalactiae and differentiate it from other beta-hemolytic streptococci

Term
How many hours after eating contaminated food do initial symptoms of staphyloccol food poisioning typically occur
Definition
2-6 hours
Term
During the past month, Staphylococcus epidermidis has been isolated from blood cultures at 2-3 times the rate from the previous year. The most logical explanation for the increase in these isolates is that:
Definition
there has been a break in proper skin preperation before drawing blood for culture
Term
An outbreak of Staphylococcus aureus has occured in a hospital nursery. In order to estabilish the epidemiological source of the outbreak, the most commonly used typing method is:
Definition
serological typing
Term
A light yellow colony from a skin leision grew aerobically and tested as catalase-negative. The organism stained a gram-positive cocci in clusters. The organism was modified oxidase positive., bacitracin (0.04U) susceptible and resistant to lysostaphin. What is the identification of this organism?
Definition
Micrococcus luteus
Term
An isolate of unknown beta-hemolytic streptococcus  is streaked perpendicular to a streak of beta-lysin-producing Staphylococcus aureus. After incubation a zone of arrowhead hemolysis is noted at the interface of the two streaks.What is the name of the test and the persumptive identification of the unknown Streptococcus :
Definition

CAMP test

S. agalactiae

Term
Which of the following may be used a a positive quality control organism for the bile esculin test.
Definition
Enterococcus faecalis
Term
Infection of the urinary tract is most frequently associated with:
Definition
Escheria coli
Term
MacConkey media for screening suspected cases of hemoragic E. coli O157:H7 must contain:
Definition
sorbital
Term
Members of the family enterobacteriaceae share which of the following characteristics:
Definition
reduce nitrate to nitrite
Term
Which of the following genera is among the least biochemically reactive members of the Enterobacteriaceae ?
Definition
Shigella
Term
Which one of the following gram negative bacilli ferments glucose?
Definition
Yersinia enterocolitica
Term

A sputum culture from an alcoholic seen in the ER grows gray, mucoid, stringy colonies on sheep blood agar. The isolates grows redily on MacConkey agar and forms mucoid, dark pink colonies. The colonies yield the following test results:

ONPG:         +

indole           -

Glucose        +

oxidase          -

citrate            +

VP                 +

 The organism is most likely

Definition

Klebsiella Pneumonaie

--++

Term

An organism was inoculated to a TSI tube and gave the following reactions:

 

alkaline slant/acid butt  H2S, gas produced

Definition
Salmonella typhimurium
Term

An isolate from a stool culture gives the following growth characteristics and biochemical reactions:

MacConkey agar: colorless colonies

Hektoen agar:  yellow-orange colonies

TSI; acid slant/ acid butt, no gas, no H2S

urea: positive

Definition
Yersinia enterocolitica
Term

A TSI tube inoculated with an organism gave the following reactions:

alkaline slant/ acid butt no H2S, no gas produced 

Definition
Shigella dyentreriae
Term

An organism gave the following reactions:

TSI:    acid slant/ acid butt, no H2S,  gas produced

indole:        positive

motility:      positive 

citrate:    negative

lysine decarboxylase:    positive

Urea:      negative

VP:  negative

This organism most likely is

Definition

Escherecia coli

++--

Term
Which of the following organisms can grow in the small bowel and cause diarrhea in children, travelers diarrhea, or severe cholera- like syndrome through the production of enterotoxins
Definition
Escherichia coli
Term
One of the enterotoxins produced by the enterotoxigenic Escherichea coli in travelers diarrhea is similar to a toxin produced by
Definition
Vibrio cholerae
Term
Shigella species characteristically are:
Definition
nonmotile
Term
A gram negative bacillus has been isolated from feces, and  the confirmed biochemical reactions fit those of Shigella. The organism does not agglutinate in shigella antisera. What should be done next?
Definition
boil the organism and retest the antisera
Term
Biochemical reactions of an organism are consistant with Shigella. A suspension is tested in: antiserum without resulting agglutination: However, after 15 minutes of boiling , agglutination occurs in group D antisera. The Shegilla species is:
Definition
sonnei
Term

>100,000 CFU/mL of a gram- negative bacilli were isolated on MacConkey from a urine specimen. Biochemical results are as follows:

glucose:                     acid, gas produced

indole:                        negative

urea:                           positive

TDA:                          positive

H2S:                           positive

The organism is most likely:

Definition
Proteus mirablis
Term

A urine culture had the following culture results:

sheep blood             swarming

Columbia CNA :     no growth

MacConkey:         1. >100,000CFU/mL nonlactose-fermenter

                              2.> 100,000 CFU/mL nonlactose-fermenter with red pigment

The isolates from MacConkey agar had the following biochemical reactions.

TEST              isolate1                 isolate2

TSI                alk/acid                 alk/acid

urea               positive                  negative

TDA              positive                 negative

H2S                positive                 negative

The organism is most likely
     

 

Definition
Proteus vulgaris and serratia marcescens
Term

An 8 year old girl was admitted to the hospital with  a three day history of fever, abdominal pain, diarrhea, and vomiting. A stool culture grew many lactose- negative colonies that yiealded the following test results.

oxidase:       negative

TSI              acid slant/acid butt

indole:         negative

urease:         positive

ornithine decarboxylase:         positive

H2S:            negative

motility at 25*C                       positive

 

Definition
Yersinia enterocolitica
Term
Which of the following sets of test best differentiates Salmonella and Citrobacter species?
Definition

(citrobacter+)KCN, malonate, beta-galactosidase,

 (salmonella+)lysine decarboxylase

Term

A fecal specimen, inoculated to Xylose lysine deoxycholate (XLD) and Hektoen enteric (HE) produced colonies with black centers. Additional testing results are as follows

 TEST      |  result             serological test       result

glucose     positive           polyvalent           no agglutination

H2S           positive            Group A             no agglutination

Lysine decarboxylase po  Group B             no agglutination

Urea          negative           Group C             no agglutination

ONPG      negative            Group D             no agglutination

Indole       positive             Group V            no agglutination

The most probable identification is:

Definition
Edwardsella tarda
Term

A 10 year old boy was admitted to the emergency room with lower right quadrant pain and tenderness. The following laboratory resuts were obtained:

                    Paitent value         normal range

% segs               75%                       16-60%

WBC count        200                       13

The admitting diagnosis was appendicitis. During surgery the appendix appeared normal; an enlarged node was removed and cultured. Small gram negative bacilli were isolated from  the room temperature plate. The organism most likely is:  

Definition
Yersinia entercolitica
Term
A 25 year old man who has had recently worked as a steward on a transatlantic  grain ship presented to the emergency room with high fever,  diarrhea and prostration. Axillary lymph nodes were hemorragic and enlarged. A Wayson strain of aspirate showed bacilli that were bipolor resembling saftey pins. The most likely identification of this organism is:
Definition
Yersinia pestis
Term
Biochemical reactions of an organism are consistant with Salmonella . A suspension is tested in polyvalent antiserum A through G and Vi antiserum. There is agglutination in the Vi antiserum only. What should be done next?
Definition
Repeat the biochemical identification of the organism.
Term

A clean catch urine sample from a nursing home patient is cultured using a .001 mL loop. It grows 67 colonies of a lactose fermenter that has the following biochemical reactions:

TSI: acid/acid

Oxidase: negative

Motility: positive

Indole: negative

Citrate: positive

VP: positive

Lysine decarboxylase: negative

Orinthine decarboxylase: positive

Urea: negative

What should the microbiologist report?

Definition
67,000 colonies CFU/mL Enterobacter cloace
Term
Plesiomonas shgellosis is a relatively new mwmber of the family Enterobacteriaceae. What characteristic separates it from other members of the Enterobacteriaceae?
Definition
it is oxidase positive
Term

A 64 year old man with lymphoma has a positive blood culture at 18 hours incubation. The organism is a nonlactose fermenting gram-negative bacillis on MacConkey agar. Further testing gives the following reactions:

oxidase: negative

TSI: alk/acid (no H2S)

motility : positive

indole: positive

citrate positive (morganella is citrate neg)

orinthine decarboxylase: negative

urea: positive

PAD: positive

VP: negative

The genus is:

 

Definition
provedencia
Term
The stock cultures that needed for quality control of motility are:
Definition
Klebsiella pneumoniae/Escherichia coli
Term
The stock cultures that needed for quality control testing of oxidase production  are:
Definition
Echericheia coli and Pseudomonas aruginosa
Term

The stock cultures that needed for quality control testing of deamination activity are:

(PAD)

Definition
Proteus mirabilis and Echericheia coli
Term
The stock cultures that needed for quality control testing of deoxyribonuclease (Dnase) production are:
Definition
Serratia marcescens/Echericheia coli
Term
Quality control of the spot indole test requires the use of ATCC cultures of:
Definition
Echericheia coli / Enterobacter cloacae
Term
An organism that exhibits the satellite phenomenon around colonies of staphylococci is:
Definition
Haemophilus influenzae
Term
An organism isolated from the surface of a skin burn is found to produce a diffusible green pigment on a blood agar plate. Further studies of the organism would most likely show the organsim to be:
Definition
Pseudomonas aruginosa
Term
A nonfermenting gram negative bacillus is isolated from a wound. The nitrate and oxidase are strongly positive. The growth on sheep blood agar has a grape like ordor. The organism is
Definition
Pseudomonas aruginosa
Term
A nonfermenting gram negative bacillis is isolated from an eye culture. It grows only on chocolate agar and is oxidase negative. The most likely organism is
Definition
haemophillus influenza
Term
A blood culture with macroscopic signs of growth is Gram stained and the technician notes small, curved gran-negative bacilli resembling gull wings. It is subcultured to blood and chocolate agar, and incubated aerobically and anaerobically. After 24 hours, no growth is apparent . The next step would be to:
Definition
subculture the bottle and incubate it in microaerophilic conditions.
Campylobacter
Term
The optimal incubator temperature for isolation of the Campylobacter jejuni/coli group is
Definition
42*C
Term

A patient with a nosocomial pneumonia has a sputum gram stain that shows many neutrophils and numerous small gram negative cocobacilli. The organism grew in 24 hours as a mucoid hemolytic colony on blood agar and a colorless colony on MacConkey agar. The organism had the following characteristics :

oxidase : negative

catalase: positive

nitrate: positive

ONPG: negative

orinthine decarboxylase: negative

lysine decarboxylase: negative

Definition
Acinetobacter baumanni
Term
A gastroenterologist submits a gastric biopsy from a patient with a gastric ulcer. To obtain presumptive evidence of Helicobacter pylori, a portion of the specimen should be added to which media?
Definition
urea broth
Term
A 4 year old boy is admitted to the hospital with suspected meningitis. He has not had most of the childhood vaccines. The suspected pathogen is:
Definition
Haemophilus influenza
Heamophilus influenza was previously the most common cause of bacterial meningitis in young children. However, the Haemophilus influenza type B vaccine has been in use for several years, resulting in a low incidence of H influenza causing meningitus. This patient has not had most childhood vaccinations, so he susceptible to H influenza.
Term
Acinetobacter Iwoffii differs from neisseria gonorrhoeae in that the former:
Definition
Will grow on MacConkey and EMB media
Both organisms are gram negative. Neisseria gonorrhoea is fastidious and does not grow on MacConkey or EMB agar, but Acinetobacter is oxidase negative.
Term
A 4 year old boy is admitted with symptoms of meningitis, and a gram stain of the cerebrospinal fluid reveals small, pleomorphic, gram-negative cocobacilli. After 24 hours incubation at 35*C, small, moist, gray colonies, which are oxidase negative, are found on the chocolate agar plate only. Which of the following biochemical data would be consistant with this isolate?
Definition

X factor no growth

V factor no growth

X and V growth

Haemophilus influenza needs X and V both.

chocolate has X and V

 

Term
A gram stain of a touch prep from a gastric biopsy shows gram-negative bacilli that are slender and curved. The most likely pathogen is:
Definition
Helicobacter pylori
Term
A cerebrospinal fluid has been inoculated onto sheep blood and chocolate agar plates and into a tube of trytocase soy broth. All media were incubated in an atmosphere of 5% CO2. Which of the following organisms would usually be isolated by this procedure?
Definition
Haemophilus influenza
Term
If present, a characteristic that is helpful in separating Pseudomonas from other members of the Pseudomonas family is:
Definition
growth at 42*C
Pseudomonas aruginosa grows at 42, but this temperature is inhibitory for other Pseudomonas.
Term

A Camplobacter species isolated from a stool culture gives the following biochemical reactions

nalidixic acid:  susceptible

cephalothin: resistant

hippurate hydrolysis: positive

Oxidase: positive

Catalase: positive

Definition
Campylobacter jejuni
Campylobacter jejuni and C. Coli are closely related and both are pathogens. The test differentiates the two is hippurate hydrolysis.
Term
Which one of the following results is typical of Campylobacter jejuni?
Definition
Optimal growth at 42*C
Campylobacter jejuni will grow at 37 but prefers 42. It is oxidase and catalase positive and motile.
Term
Optimum growth of Campylobacter jejuni is obtained on suitable media incubated at 42*C in an atmosphere containing
Definition
6% O2, 10-15% CO2, 85-95% nitrogen? Campylobacter is microaeroplilic, and requires a decreased oxygen and increased carbon dioxide atmosphere for growth.
Term
The porphyrin test was devised to detect strains of Haemophilus capable of:
Definition
synthesis of hemin
The porphyrin test is an alternative method for detecting heme-producing species of Haemophilus. It detects whether or not the organism converts the substrate delta amino levulinic acid into porphyrins or porphobilinogen, which are intermediates in synthesis of factor X.
Term
Haemophilus influenza is most likely considered normal indigenous flora in the:
Definition
oropharynx
Upper respiratory tract.
Term
Haemophilus influenza becomes resistant to ampicillin when the organism produces a:
Definition
beta-lactimase enzyme
the beta-lactamase enzyme produced by Haemophilus influenza inactivates the antibiotics that have a beta-lactam ring in their structure, such as penicillins and cephalosporins.
Term
An isolate on chocolate agar from a patient with epiglotitis was suggestive of Haemophilus species. Additional testing showed that the isolate required NAD for growth and was nonhemolytic. The organism is most likely haemophilus:
Definition
parainfluinza Haemophilus parainfluenza requires NAD for growth but not Hemin. This distinguishes it from H. Influenzae. H. Haemolyticus is hemolytic, and H. Ducreyi does not cause epiglotitts.
Term
Which of the following specimens is considered to be the most sensitive for the recovery of Brucella in cases of chronic infection?
Definition
bone marrow Bone marrow is considered the most sensitive specimen for the recovery of brucella
Term

A genus that is found in soil and water and causes infection in immunocompromised patients has the following characteristics:

sheep blood agar: violet pigment

MacConkey agar: growth

42*C incubation: growth

Oxidase: Postive

OF glucose: fermenter

indole: negayive

The Genus is:

Definition

Chromobacterium

the purple color on blood gives this away

Term
Which of the following results is typical of Campylobacter fetus subspecies fetus?
Definition
Growth at 37*C
Term

Multiple blood cultures from a patient with endocarditis grew a facultative anaerobic, pleomorphic gram- negative bacilli with the following characteristics:

hemolysis; negative

MacConkey agar:  no growth

Sheep blood agar: growth in 5%-10% CO2

chocolate agar: : growth in 5%-10% CO2

catalase : negative

V factor: not required

X facter: not required

oxidase: negative

Nitrite:   positive

Indole:    negative

The most likely identification is:

Definition
Haemophilus aphrophilus
Term

A gram negative bacillus with bipolor staining was isolated from a wound infection caused by a bite from a pet cat. The following characteristics reactions were seen:

oxidase: positive

glucose OF: fermentive

catalase: positive

motility: negative

MacConkey agar:    no growth

Which of the following is the most likely organism?

 

Definition
Pasturella multicida
Term
A culture from an infected dog bite on a small boys finger yielded a small, gram negative cocobacillus that was smooth, raised and beta-hemolytic on blood agar. The isolate grew on MacConkey agar, forming colorless colonies. The organism was motile, catalase positive , oxidase positive, reduced nitrate and was urease positive within 4 hours. No carbohydrates were fermented. The most likely identification is;
Definition

Bordetella bronchiseptica

 

pasturella multicida does not grow on MacConkey,and  is not motile

Term
While swimming in a lake near his home, a young boy cut his foot, and an infection developed. The culture grew a nonfastideous gram-negative , oxidase positive , beta-haemolytic, motile bacilli that produced deoxyribinose. The most likely identification is:
Definition

Aeromonas hydrophilia

Wounds contaminated with water

Term

An aerobic, gram negative cocobacillus was isolated on Bordet-Gengou agar from a nasopharyngeal swab 48 hours after culture from a 6 month-old infant with suspected pertusis. The organism exhibited the following characteristics:

MacConkey agar: no growth

Urea:  negative at 4 houes, positive at 24 hours

Oxidase negative

catalase: positive

The most probable identification of this isolate is:

Definition

Bordetella pertussis

The oxidase and urea reactions differentiate Bordetella pertussis aand B parapertussis.

B pertussis is oxidase positive and urea positive

Term
Which of the following characteristics best differentiates Bordetella bronchiseptica from Alcaligenes species?
Definition

rapid hydrolysis of urea

 

bordeletella bronchiseptica is urease positive in 4 hours.

Term
Serum samples collected from a patient with pneumonia demonstrate a rising antibody titer to Legionella. A broncheoalveolar (BAL) specimen from this patient has a positive antigen test for Legionella but no organisms were recovered on buffered charcoal yeast extract medium after 2 days of incubation. The best explanation is that the :
Definition

culture was not incubated long enough

 

Media for isolation of Legionella should be incubated 235-37*c FOR AT LEAST 7 DAYS.

Term
Which characteristic best differentiates Acinetobacter species from Moraxella species?
Definition

Production of indophenol oxidase.

Both Acinetobacter and Moraxella display resistance to penicillin, and some species grow on MacConkey agar. Acinetobacter are oxidase negative, and Moraxella are oxidase positive

Term
An organism has been identified as a member of the fluorescent group of pseudomonas, Which of the following sets of test should be used to determine the species of the organism?
Definition

Growth at 42*C, pyocyanin, gelatinase production.

gelatinase production separates Pseudomonas putida (negative) from Pseudomonas Fluorescence (positive)

Term
Appropriate culture requirements for a patient suspected of having  tularemia include:
Definition
A media with cysteine , such as buffered charcoal yeast extract agar
Term

A child was bitten on the arm by her sibling and the resulting wound grew a slender gram-negative bacilli that has the following characteristics:

growth on SBA:  colonies that pit the agar

colonies odor: like bleach

Catalase:  negative

oxidase: positive

TSI: no growth

The identification of this organismis:

Definition

Eikenella corrodens

Pitting the agar and smell of bleach

Term
Characteristics of the genus Capnophagia include:
Definition

colonies are large and spreading after 2 days.

 

Capnocytophagia requires increased CO2 , fermenta glucose, sucrose, and lactose, and is a gram negative bacillus. Capnopcytophagia produces characteristic spreading colonies.

Term
A laboratory aid recieves a bronchoscopy sample with the request for culture of Legionella. The assistant she asks a microbiologist for direaction on plating protocol. The correct response from the microbiologist is: 
Definition
Culture on buffered charcoal yeast extract agar with antibiotics
Term
A community hospital microbiology laboratory is processing significant numbers of stool cultures because of an outbreak of diarrhea following heavy rains and flooding in the country. A media that should be incorperated in the plating protocol is:
Definition
Thiosulfate citrate bile salts sucrose for vibrio species
Term

A college student attended a beach party where raw oysters and other shellfish were consumed. The next day, he had symptoms of septicemia. The blood cultures grew gram negative bacilli with the following characteristics:

oxidase: positive

MacConkey agar: pink colonies

O/129 (ug):  susceptible

The most likely organism is:

 

Definition

Vibrio vulnificans

vulnificans is the only vibrio that ferments Lactose

Term
Differentiating test that will separate Burkholderia from Stenotrophomonas inclue:
Definition

oxidase

Stenotrophomonas is oxidase negative while most other nonfermenters are ocidase positive

Term

A 17 year old female with cystic fibrosis is diagnosed with pneumonia. A sputum sample grew gram negative bacilli with yellow, smooth colonies that have the following biochemical reactions:

oxidase: positive

TSI: alk/alk

glucose: oxidized

fluorescence: negative

Lysine decarboxylase positive

The most likely organism is:

Definition

Burkholderia cepatia

Berholderia cepatia is associated with respirtory infections  in cyctic fibrosis patients, and the biochemicals are typical for this organism.

Term
Characteristic of the HACEK group of bacteria include:
Definition

requirement  of 5%-10% CO2 for growth.

The HACEK group of organisms are gram negative bacilli that require increased CO2 for growth. They are commonly associated with endocarditis, and include Haemophilus species (especially H.Aphrophilus), Actinobacillus actinomycetmcomitans, Cardiobacterium hominis, Eikenella corrodens and Kingella species.

Term

The Laboratory recieves a blood culture from a veterinarian who has been ill for many weeks with fevers in the afternoon and evenings, arthritus, and fatigue. The blood culture is positive after 5 days , and the organism has the following characteristics:

Gram stain: small gram negative cocobacilli

sheep blood agar: growth after 48 hours with small, smooth, raised colonies

What should the microbiologist do next:

 

 

Definition
Take extra saftey precautions for brucella
Term
The primary isolation of Neisseria gonorrhoeae requires:
Definition
carbon dioxide
Term
Assuming the agent isolated from a patients spinal fluid produces a positive oxidase test, the most likely diagnosis is:
Definition
meningococcal meningitis
Term

The following results were obtained from a culture of unknown origin:

Gram stain: gram negative diplococci

indophenol oxidase : positive

glucose: poositive

Maltose:  negative

Sucrose: negative

The most likely source of the specimen would be the:

Definition
Genitourinary tract
Term
A ureatheral swab obtained from a man with a uretheral exudate was plated directly on chocolate agar and modified Thayer Martin agar, and a gram stain was made . Thr gram stain showed gram negative diplococi. The culture plates were incubated at 35*C, but had no growth at 48 hours. The most likely failure for organism growth is that the: 
Definition
Organism rerqiures CO2 for growth.
Term
A gram stain performed on a sputum specimen revealed gram -negative dipilococci within PMNs. Oxidase testing is positive and carbohydrate degredation test are inert. The organism is:
Definition

Moraxella catarrhalis

(all other niesseria ferment carbohydrates)

Term
Coagglutination is associated with:
Definition

Neisseria gonorrhea

One of the less commonly used methods for identification of neisseria gonorrhoeae grown in culture is coagglutination

Term
Clinical resistance to penicillin coorelates most frequently with beta-lactamase production in:
Definition
Niesseria gonorrhea
Term
All of the species of the genus Neisseria have the enzyme to oxidize:
Definition

tetramethyl-phenylenediamine

(they are all oxidase positive)

Term
The diagnosis of Neisseria gonorrhoeae in females is best made from:
Definition
An endocervical culture
Term

A vaginal smear is submitted for a gram stain for niesseria gonorrhoea. The technologist finds the following results on the gram stain:

many white blood cells

few epithelial cells

many gram postitve cocci

few gram negative diplococci

few gram positive cocci in chains

The technologist should :

Definition
 Not read or report a gram stain on a vaginal specimen
Term
Which of the following is the most reliable test to differentiate Neisseria lactamica from Neisseria meningidis?
Definition

lactose degradation

 

Neisseria lactamica ferments lactose, Neiserria meningidis does not.

Term
Definitive identification of Neisseria gonorrhea is made with the:
Definition
Hydrolysis of carbohydrates
Term
A gram-negative diplococcus that grows on modified Thayer Martin medium can be further confirmed as Neisseria gonorrhoea if it is:
Definition
oxidase positive and glucose positive, maltose negative
Term
An organism previously thought to be non-pathogenic, Moraxella catarrhalis, is now known to be associated with oppertunistic respiratory infection and nosicomial transmission. Characteristic identification  criteria include:
Definition

Carbohydrate negative

(asaccharolytic)

Term
An autopsy performed on an 8 year old child revealed Waterhouse-Freidrickson syndrome. Blood and throat cultures taken prior to death were positive for which organism?
Definition
Neisseria meningitidis
Term

An aspirated specimen of purulent material was obtained from a brain abcess. After 24 hours incubation , pinpoint colonies grew on sheep blood and small yellowish colonies grew on chocolate. Gram stain of the organism showed gram negative cocci. Results of carbohydrate degradation studies were as follows:

glucose: acid

maltose: acid

sucrose: acid

lactose: negative

Additioonal testing revealed that the organism was oxidase positive and beta-galactosidase negative. The organism is most likely Neisseria:

Definition

sicca

 

the only one listed that ferments glucose, maltose, and sucrose

Term

****************GPB**********************

A gram stain of organisms on Loffler agar showed pleomorphic gram-positive bacilli.The organism should be subcultured to:

Definition

potassium tellurite

 

(corynebacterium diptheria)

Term
Which organism commonly causes food poisioning by consumption of foods containing excessive population of organisms or preformed enterotoxin?
Definition
Bacillus cereus
Term

An organism recovered from a sputum has the following characteristics:

Culture:  growth at 7 days on lowenstein-jensen agar, incubated under aerobic conditions with CO2  at 35*C.

Gram-stain:  delicate branching gram-positive bacilli

acid-fast staining:   Branching, filimentous , "partially" acid fast bacterium

These results are consistant with which of the following genera?

Definition
Nocardia
Term
The best procedure to differentiate Listeria monocytogenes from Corynebacterium species is:
Definition
motility at 25*C
Term
Establishing the pathogenicity of a microorganism isolated from a childs throat and identified as Corynebacterium diptheria would depend upon:
Definition

a positive toxigenicity test In order to determine if an isolate of Corynebacterium diptheria produces toxin,

testing for the presence of diptheria toxin must be performed using methods such as the Elek test or PCR

 

Term
Which features distinguishes Erysipelothrix from other clinically significant non-sporeforming, gram positive , facultatively anaerobic bacilli?
Definition

H2S production

the only one

Term
Listeria can be confused with some streptococci because of its haemolyisis and because it is:
Definition

esculin positive

 

Ummm...its a GPB???

Term
Fluid from a cutaneous black lesion was submitted for a routine bacterial culure. After 18 hours of incubation at 35*C there was no growth on MacConkey agar, but 3+ growth on sheep blood agar. The colonies were non-hemolytic, nonmotile, 4-5 mm in diameter and off white with a ground glass appearance. Each colony had an irregular edge with comma shaped outgrowths that stood up like"beaten egg whites"when gently lifted  with an inpculating needle. A gram stain of a typical colony showed large, gram-positive retangular bacilli, The organism is most likely:
Definition

Bacillis antracis.

 

NON-HEMOLYTIC and NON-MOTILE

Term
A branching gram positive. partially acid-fast organism is isolated from a brochhial washing on a 63 year old woman recieving chemotherapy. The organism does not hydrolyse casein, tyrosine or xanthine. The most likely identification is:
Definition

Norcardia asteriodes.

 

Term

*****************ANAEROBES*****************

The characteristic that is most commonly associated with the persence of strict anaerobic bacteria and can be taken as presumtive evidence of their presence in a clinical specimen is the:

Definition
presence of a foul, putrid odor from tissue specimens and cultures
Term
Gram stain of a thigh wound showed many gram-positive spore forming bacilli.The specimen was placed on brain heart infusion blood agar and incubated aerobically at 35*C for 3 days.At the end of that time , the plates showed no growth. The most likely explanation  is that some of the specimen should have been incubated:
Definition
anaerobically
Term
An aspirate of a deep wound was plated on blood agar aerobically and anaerobically. At 24 hours there was growth on the anaerobic plate only. The next step in the evaluation of this culture is to:
Definition
begin organism identification
Term
Anaerobic infections differ from aerobic infections in which of the following?
Definition
they are usually Polymicrobic
Term

The following growth results were observed on media inoculated with a foot abcess aspirate and inoculated in 3%-5% CO2.

SBA: 2+ large gray colonies

PEA:  no growth

chocolate:   3+ large gray colonies

MacConkey:  3+ lactose fermenters

trytocase soy broth: gram negative bacilli and gram-positive bacilli

 Biochemicals were set up on the colonies from the MacConkey agar plate. What should the microbiologist do next?

Definition
Subculture TSB to SBA aerobic and SBA anaerobic.
Term
Which of the following pairs of organisms usually grow on kanamycin, vancoumycin, laked blood agar?
Definition
Bacteroides and prevotella
Term
Acceptible specimens for culture of anaerobic bacteria that cause disease include:
Definition
abscesses
Term
Proprionibacterium acnes is most often associated with:
Definition
blood culture contamination
Term
The etiologic agent of botulism is
Definition
an endotoxin producer
Term
A strict anaerobe that produces terminal spores is
Definition
clostridium tetani
Term
An anaerobic spore forming , nonmotile, gram positive, bacillus isolated from a foot wound is most likely:
Definition
Clostridium perfringens
Term
The lab has been using a latex agglutination assay to detect Clostridium difficile in stools, which identifies a non toxin cell wall antigen. The lab is considering adoption of an EIA method that detects Clostridium difficile toxin A. Which of the following would provide the best compairison? 
Definition

latex agglutionation vs culture on cycloserine cefoxitin egg-fructose agar

(the gold standard for toxin detection)

Term
The reverse CAMP test , lecthinase production , double zone of hemolysis, and Gram-stain morphology are all useful criteria in the identification of:
Definition
Clostridium perfringens
Term
Which one of the following anaerobes is inhibited by sodium polyanethiol sulfate (SPS)?
Definition
peptostreptococcus anaerobius
Term
At the persent time Clostridium difficile toxin can be detected by:
Definition
EIA
Term
An anaerobic gram-positive bacili with subterminal spores was isolated from a peritoneal abscess. The most likely identification of this organism is:
Definition
Clostridium septicum
Term
The most meaningful laboratory procedure in confirming the diagnosis of clinical botulism is:
Definition
demonstration of toxin in the patients serum
Term
A stool sample is sent to the laboratory for culture to rule out Clostridium difficile. What media should the microbiologist use and what is the appearance of the organism on this media?
Definition
CCFA yellow, ground glass colonies.
Term
A gram stain of drainage from a pulmonary sinus tract shows many WBCs and 3+ branching gram positive bacilli. Colonies grow on anaerobic media after 3 days incubation. They are yellow tan and have a molor tooth appearance. The most likely genus is:
Definition
Actinomyces
Term
Which organism is the most common anaerobic isolated from infectious processes of soft tissue and anaerobic bacteremia?
Definition
Bacteroides fragilis
Term
Which of the following genera include anaerobic gram negative non-sporeforming bacilli?
Definition
Bacteroides
Term
An organism from a peritoneal abscess is isolated on kanamycin-vancoumycin laked blood agar and grows black colonies on BBE agar. It is nonpigmented, catalase positive, and indole negative. The genus of this organism is:
Definition
Bacteriodes
Term
Which of the following sets of organisms may exhibit a brick red flourescnce?
Definition
Veilonella parvula and Prevotella melaninogenica
Term
Which of the following sets of organisms may exhibit brick red flourescesce ?
Definition
Vionella paruva and Prevotella melaninogenia
Term

A 1-2 mm translucent, nonpigmented colony, isolated from an anaerobic culture of a lung abscess after 72 hours, was found to flouresce brick-red inder ultra-violet light. A gram stain of the organism revealed a cocobacillus that had the following characteristics:

growth in bile: inhibited

vancoumycin: resistant

kanamycin: resistant

colistin: susceptible

esculin hydrolysis: negative

indole: negative

The identification of this isolate is:

Definition
Provotella melaninogenica
Term
A thin gram-negativebacillus with tapered ends isolated from an empyema specimen grew only on anaerobic sheep blood agar . It was found to be indole positive, lipase negative, and was inhibited by 20% bile. The most probable  identification of this isolate would be?
Definition
Fusobacterium nucleatum
Term
Which of the following anaerobes would be negative for indole?
Definition
Bacteriodes fragilis
Term
The presence of 20% bile in agar will allow growth of:
Definition

Bacteriodes ovatus

 

Term
A control strain of Clostridium should be used in an anaerobic jar to assure:
Definition
That ananaerobic enviroment is achieved.
Term
Which of the following organisms could be used as the positive quality control test for lacthinase on egg yolk agar?
Definition
Closteridium perfringens
Term

*****************FUNGI*******************

The major features by which molds are routinely identified are:

Definition
Macroscopic characteristice and microscopic morphology
Term
A sputum specimen from a patient with a known Klebsiella pneumoniae infection is recieved in the laboratory for a fungus culture. The proper procedure for handling this specimen is to:
Definition
include media that have cyclohexamide and chloamphenocol added to inhibit bacteria
Term
Many fungal infections are transmitted to man via inhalation of infectious structures. Which of the following is usually contracted in this manner?
Definition
Histoplasma capsulatum
Term
A smear of skin tissue reveals fluorescent septate hyphae. The smear was prepared using:
Definition
calcaflour white
Term
Anti-fungal susceptbility test for yeast are:
Definition
more useful in identifying resistant strains
Term
In perparing an india ink slide, the technician should ensure that the :
Definition

Proper amount of reagent is added.

too much india ink blocks transmission of light.

Term

An organism that demonstrates budding yeast cells with wide capsules in an india ink preparation of spinal fluid is probably:

 

Definition

Cryptococcus neoformans

Cryptococcus neoformens is a cause of meningitus in immunocompromised patients, and produces a polysaccharide capsule.

Term
The formation of a germ tube presumptively identifies:
Definition

Candida albicans

(Candida albicans produces germ tubes)

Term
A HIV positive patient began to show signs of meningitus. A spinal fluid was collected and cultured for bacteria and fungus. A budding encapsulated yeast was recovered. Which organism is consistant with this information?
Definition

Crytococcus neoformans

 

is a cause of meningitis in immunocompromised patients, and produces brown colonies (due to melanin production) on bird seed agar.

Term
Staib medium (birbseed agar) is useful in the identification of which of the following?
Definition
Crytococcus neoformans
Term
Gram stain examination of a CSF specimen indicates the presence of yeast like organisms with gram positive granular inclusions . Which of the following techniques should be used next to assist in the identification of this organism?
Definition

India ink

 Cryptococcus neoformans may not stain well on Gram stain. Rapid identification is important when yeast is dected in CSF the presence of capsules seen in an indian ink preparation would be presumptive for C neoformans.

Term
The one characteristic by which an unknown Cryptococcus species can be identified as a Cryptococcus neoformans is:
Definition

positive phenol oxidase test.

Cryptococcus neoformans is the only clinically encountered yeast that is phenol oxidase positive.

Term

A urine culture from a patient with a urinary tract infection yields a yeast with the following characteristics:

Failure to produce a germ tube

hyphae not formed on cornmeal agar

urease negative

assimilates trehalose

The most likely identification is:

Definition

Candida glabrata

of the yeast listed only Candida glabrata is urease negative and does not produce a germ tube.

Term

A yeast isolate from a CSF specimen produced the following results:

India ink: no encapsulated yeast cells

Cryptococcal antigen: negative

Urea: negative

Germ tube: negative What should the technologist do next?

 

Definition

carbohydrate assimilation

 

Conventional test such as carbohydrate assimilation , must be performed for definitive identification of the yeast in this  CSF specimen , especially in light of the fact that the yeast is both crypticoccal antigen and germ tube negative.

Term
The recovery of cryptococcus species may be compromised if the isolation media contains:
Definition

Cyclohexamide

 

Cyclohexamide is known to inhibit the growth of some fungal pathogens, including Cryptococcus neoformens

Term

A neonatal blood culture collected through a catheter grows a small yeast, Microscopically, the yeast apear round at one end , with a budlike structure on a broad base at the other end. Growth is enhanced around olive oil saturated discs, The organism isolated is:

 

Definition

Malassezia furfur

Malsssezia furfur cause catheter-related sepsis, requires lipids for growth, and is a small yeast with a wide bud.

Term
Two blood cultures are positive for yeast from a patient with an intravenous catheter. One culture grew Candida albicans, while the other grew Candida Krusie. Which medium should the technologist use to subculture the blood bottles to in order to verify that the cultures are pure?
Definition

chromogenic agar

 

Chromogenic agar is extremely effective in determining mixed yeast populations in clinical specimens.

Term
Quality control testing of CHROMEagar, Candida medium shows very weakly colored colonies after incubation at 25*C, ambient atmosphere for 48 hours . The technologist should
Definition

repeat the quality control test , but incubate at 35*C

CHROMagar produces the best color development when incubated at 35-37*C

Term

The morphological characteristics of a yeast grown in rabbit plasma are shown in the image :

[image]

The most likely identification of this yeast is:

 

Definition

Candida albicans

Candida albicans produces a tubular structure with no constrictions (germ tubes) when incubated in rabbit plasma

Term
The most sensitive test for the diagnosis of cryptococcal disease is:
Definition

Cryptococcal antigen

Cryptococcal latex antigen test has been proven to be significantlybmore sensitive than staining methods.

Term
Which of the following statements concerning the germ tube test is true?
Definition
Candida albicans(positive) and candida tropicalis(negative) can be used as positive and negative controls
Term
Which of the following procedures should be performed to confirm that an unknown mold is one of the pathogenic dimorphic fungi:
Definition

culture conversion to yeast form

 

Several monomorphic molds resemble the filamentous phase of dimorphic molds, so conversion to yeast phase must be performed for identification of dimorphic molds.

Term
Lab workers should always work under a biological safety hood when working with cultures of:
Definition

Coccidioides immitis

The arthroconidia of Coccidiodies immitis produce alternating arthrospores.

Term
Structures important in the microscopic  identification of coccidiodes immitus are:
Definition
irregular staining , barrel shaped arthrospores.
Term
Which of the following is the most useful morphological feature in identifying the mycealial phase of histoplasma capsulatum?
Definition

8-14 tuburculate macroconidia

The presence of turberculate macroconidia indicates a presumptive identification of H capsulatum. The identification must be confirmed using nucleic acid probes or exoantigen testing

Term
A mold grown at 25*C exhibited delicate septate hyline hyphae and many conidiphores extending at right angles from the hyphae Oval , 2-5 um conidia were formed at the at the end of the conidiphores giving a flower like appearance. In some areas sleeves of spores  could be found along the hyphea as well. A 37*C culture of this organism produced small cigar shaped yeast cells. This organism is most likely:
Definition

Sporothrix shencki

[image]

 

Term
A fungal isolate from the sputum of a patient with a pulmonary infection is suspected to be Histoplasma  capsulatum . Tuberculate macroconidia were seen on the hyphae of the mold phase, which was isolated at room temperature on Sabouraud dextrose agar containing chloramphenocol and cyclohexamide (SDA-CC). A parallel set of cultures incubated at 35*C showed bacterial growth on SDA, but no growth on SDA-CC. Which of the following is the appropriate course of action?
Definition

Subculture the mold phase to moist BHI blood media, incubate at 25*C

Dimorphism differentiates Sporothrix from other fungi listed.

 

Term

Skin scrapings obtained from the edge of a crusty wrist leision  were found to contain thick walled sherical yeast cells (8-15 um in diamater) that had single buds with a wide base of attachment, Microscopic examination of the room temperature isolate from this specimen would probably reveal: 

[image]

Definition

round or pear shaped small conidia attached to conidiphores of irregular lenghts.

(blastomyces)

Term

Examination of a fungal culture form a bronchial washing reveals white, cottony areial mycelium. A tease preparation in lactophenol cotton blue shows the structure shown in the image:

[image]

The most rapid test for definitive identification is:

Definition

nucleic acid probes

(coccidoides immitis)

Term
Penicillum species is isolated from a bone marrow culture of a patient that travelled to southwest Asia. After 7 days in the isolate produces a red pigment that diffuses into the medium.The technologist should.
Definition

transfer a colony to BHI at 35*C

penicillim marneffei

Pennicillim marneffei is a dimorphic fungi that produces a diffusible red pigment.

Term
The microscopic structures that are most useful in the identification of dermatophytes are:
Definition

macroconidia and microconidia

Dermatophites include 3 genera that are generally differentiated by their macroconidia formation.

Term
Which of the following is most often used to prepare a slide form a plate culture of a dermatophyte for microscopic observation?
Definition

lactophenol cotton blue

Lactophenol cotton blue is used as the mounting medium, since lactic acid acts as a clearing agent, phenol acts as a killing agent, glycerol prevents drying, and cotton blue gives color to the structures.

Term
A specimen of hair the flouresced under a wood lamp was obtained from a child with low grade scaling lesions of the scalp. Cultures revealed a fungus with mycelium and very few macroconidia or microconidia. The fungus is most likely:
Definition

Microsporum audounii

The absence of conidia differentiates Microsporum audounii from the other dermatophytes listed.

Term
Which of the following is the best aid in the identification of Epidermiphyton floccosum?
Definition
smooth walls clubbed shaped
Term
Culture of a strand of hair that fluorsced yellow-green when examined with a woods lamp produced a slow growing , flat gray colony with a salmon pink reverse. Microscopic  examination demonstrated raquet hyphae, pectinate bodies, chlamdophores, and a few abortive or bizzarre shaped macroconidia. The most likely identification  of this isolate is:
Definition

Microsporum audounii

[image]

Hair that flouresces yellow-green under a Woods lamp indicates the presence of a Microsporum species. The colony morphology and microscopic characteristics  are consistant with M audounii.

Term
On day 3 of a fungal culture , grayish cottony growth is observed that is filling the container. The most likely mold isolate is:
Definition

zygomycete

Zygomycete grow rapidly and fill the dish with cotton-candy like growth

Term
The appropriate specimen for the diagnosis of mucormycosis is:
Definition

eschar biopsy

Mucormycosis is an agressive infection where biopsy, curettage or fine needle aspiration is essential for diagnosis.

Term

Pennicillum can best be separated from aspergillus by:

 

Definition

arrangement of conidia and conidiphores

Microscopic morphology (arrangement of the conidia on the conidiophore) is used to differentiate Penicillum from aspergillus.

Term
A fungus specifically resembels penicillum species but may be differentiated because its phialides are long and tapering and bend away from the central acis. The most probable identificationis:
Definition

Paecilomyces

Elongated and tapered phialides (tenpins) are characteristic of Paecilomyces.

[image]

Term

 

[image]

An isolate from a cornea infection had the following culture results :

Sabouraud dextrose: white and cottony at 2 days , rose color at 6 days.

Slide culture: slender cycle shaped microconidia

The most likely  organism is:

 

Definition

Fusarium

Fusarium freuquently cause corneal infections and have sickle-shaped macroconidia

[image]

 

Term
In the USA, the most common organism causing eumycotic mycetoma is:
Definition

Pseudalleschereria boydii

Mycetoma,  is a slow-growing bacterial or fungal infection focused in one area of the body, usually the foot. The infection is characterized by an abnormal tissue mass beneath the skin, formation of cavities within the mass, and a fluid discharge. As the infection progresses, it affects the muscles and bones; at this advanced stage, disability may result.

Term
Crust from a cauliflower like leision on the hand exhibited brown spherical bodies 6-12um in diameter when examined microscopically. After 3 weeks of incubation at room temperature , a slow growing black mold  grew on Saubouraud dextrose agar. Microscopic examination revealed Cladosporium, Philophora and Fonsecaea types of sporulation. The probable identification of this organism is:
Definition

[image]

Fonsecaea pedrosoi

only Fonsecaea pedrosoi produces Clalosporium, Philophora and Fonsecaea types of sporulation simutaneously.

 

Term
Pus from a draining fistula on a foot was submitted for culture. Gross examinaton of the specimen revealed the presence of a small (0.8mm in diameter). yellowish, oval graunle. Direct microscopic examination  of the crushed granule showed hyphae 3-4 um in diameter and the presence of clamdospores at the periphery . After two days a cottony, white mold was seen that turned gray with gray to black reverse after a few days. When viewed microscopically, moderately large hyline septate hyphae with long or short conidiophores, each with a single pear shaped cionidium, 5-7 x 8-10um were seen. The most likely identification is:
Definition

Pseudallescheria boydii

[image]

Term
In processing clinical specimens and fungal isolates , laboratory workers may contact systemic fungal infections through:
Definition

inhalation

Specimens from fungal culture should be processed in a biological saftey cabinet to minimize the potential for aerosol spread

Term
A sputum specimen recieved at 8 am for an AFB smear reveals acid fast bacilli. An additional sputum is submitted that afternoon. This specimen was concentrated by the NALC-sodium hydroxied method and inoculated on 2 Loewnstein -Jensen slants and held for  8 weeks at 35*C in 5-10% CO2. No growth occurs. The best explanation is that:
Definition

An improper specimen was submitted for culture.

Early morning sputum specimens are optimal for AFB cultures.

Term
The preferred carbon source for mycobacteria is:
Definition

glycerol

(mycobacteria use glycerol as a carbon source in the presence of mineral salts).

Term
The first morning sputum is recieved for culture of mycobacteria. It is digested and concentrated by the  N-aceytal-L-cystine alkali method. Two Lowenstein jensen slants are incubated in the dark at 35*C with 5-10% CO2. The smears reveal acid fast bacilli, and after 7 no growth appears in the slants . The best explanation is?
Definition

cultures are held for an insufficient length of time.

Many species of mycobacterium are slow growing and may take up to 12 weeks for growth.

Term
A first morning sputum is recieved for Acid fast culture. The specimen is centrafuged, and the sediment is innoculated on two Lowenstein jensen slants, which are incubated at 35*C with 5-10% CO2, After 1 week the slants show abundant growth over the entire surface. Stains reveal gram-negative bacilli. To avoid this problem: 
Definition

decontaminate the specimen with sodium hydroxide.

Specimens contaminated by normal flora must be decontaminated prior to innoculation of media; NaOH is the most common decontaminate.

Term
A first morning sputum is recieved for culture of Acid fast bacilli. It is digested and concentrated by the  N-aceytal-L-cystine alkali method.Two Sabouraud dextrose slants are incubated in the dark at 35*C with 5-10% CO2. The smears reveal acid-fast bacilli, but the slants show no growth after 8 weeks, The explanation is:
Definition

Improper media was used.

Sabouraud dextrose slants are fungal media; mycobacteria media should have been inoculated.

 

Term
In reviewing the number of mycobacterium isolates for the current year; it was noted that there were 76% fewer isolates than the previous year (115 vs 28). The technoloist in charge of the area has documented that the quality control of the media, reagents and stains has been acceptible and there has been no gross contamination of the cultres noted. The most appropriate course of action to pursue would be:
Definition

Review the digestion and decontamination procedure.

The concentration of sodium hydroxyide may be too strong to decrese recovery of AFB and lack of contaminated cultures.

Term
Which of the following combinations of media provides an egg base, agar base, and a selective egg or agar based media.
Definition
Lowenstein jensen(egg), Middlebrook 7H11(agar), Lowenstein jensen Gruft(egg or agar)
Term
Which of the following reagents should be used as a mucolic, akaline  reagent for digestion and decontamination  of a sputum for mycobacteria culture?
Definition
N-acetly-L-cystine and NaOH
Term

The function of

N-acetly-L-cystine and NaOH In the reagent for acid-fast digestion -decontamination procedure is to:

Definition

liqufy the mucus

N-acetly-L-cystine (NALC) is a mucolic agent; the concentration of NALC may be increased to digest thick , mucoid specimens. 

Term
When staining acid fast bacilli with truant auramine-rhodamine  stain, potassium permanganate is used to:
Definition

quenching agent

The counter stain acts as a quenching agent and reduces the background flourescence of culture debries

Term
Middlebrook 7H10 and 7H11 media must be refrigerated in the dark, and incubated in the dark as well. If these conditions are not met , the media may prove toxic for mycobacterium because:
Definition

Formaldehyde may be produced

(Which is toxic to mycobacteria)

Term
The method for processing specimens for mycobacterial culture contaminated with Pseudomonas is:
Definition

Oxalic acid

The oxalic acid method is superior to alkali methods for processing specimens contaminated with Pseudomonas.

Term
An AFB broth culture is positive for acid fast bacilli at 1 week while the agar slant shows no growth. The most likely explanation for this is:
Definition
AFB grow more rapidly in liquid media
Term
A bronchial washing is processed for acid-fast bacilli. Which of the following precautions should be taken in order to prevent infection of laborotory personnel?
Definition
Process all specimens in a biological hood
Term
Tubercle bacilli are specifically stained by:
Definition

carbol fusion

Mycobacterium form stable complexes with Kinyoun carbol fusion

Term
The species of mycobacteria that will give a positive niacin test is Mycobacterium:
Definition

Tuberculosis

a positive niacin reaction differentiates Mycobacterium tuberculosis from M leprae, M kansasii and M fortuitum.

Term
A digested and decontaminated sputun is inoculated into a Bactec 12B bottle and incubated in air at 37*C. On day 14, positive growth index is obtained, and the auramine-rhodamiine stain is positive. Broth from the initial bottle is inoculated into one-Bactec 12B bottle, and one Bactec 12B bottle with NAP. After incubation, the inoculated growth bottle shows an increase in growth index, while bottle containing NAP shows no increase. The organism cultured from the sputum is most likely Mycobacterium:
Definition

Tuberculosis

Mycobacterium tuberculosis and Mycobacterium bovis cannot grow in the presence of NAP.

Term
On a culture suspected to be mycobacteium tuberculosis, the most important test to preform is:
Definition

niacin production

 A positive niacin test differentiates Mycobacterium tuberculosis from most other mycobacteria.

Term
A positive niacin test is most characteristic of Mycobacterium :
Definition

tuberculosis

Growth rate, colony morphology,and niacin reduction differentiate Mycobacterium tuberculosis from other mycobacteria 

Term
Characteristics necessary for the definitiive identification of Mycobacterium tuberculosis are:
Definition

rough, nonpigmented colony, slow growth at 37*C, niacin production-positive, nitrate production positive

tuberculosis

Growth rate, colony morphology,and niacin reduction differentiate Mycobacterium tuberculosis from other mycobacteria

Term
A two week old culture of a urine specimen produced a few colonies of acid-fast bacilli, which were rough and nonpigmented. The niacin test was weakly positive and the nitrate test was positive. Which of the following is the most appropriate action when a presumptive identification has been requested as soon as possible?
Definition
Wait a few days and repeat the niacin test; report presumptive Mycobacterium tuberculosis if the test is more strongly positive.
Term
The disease producing capacity of Mycobacterium tuberculosis depends primarily upon:
Definition

Capacity to withstand intra-cellular digestion by macrophages.

Mycobacterium can remain viable but dormant in macrophages for many years.

Term
Which species of mycobacterium includes a BCG strain used for vaccination aginst tuberculosis?
Definition

bovis

Mycobacterium can remain viable but dormant in macrophages for many years.

Term
AFB smear positive respiratory specimens may be reliably identified as mycobacterium  tuberculosis the same day the smear was read by:
Definition

nucleic acid amplification test

(PCR)

 

Several commercial PCR tests are available that identify Mycobacterium tuberculosis from positive respiratory specimens.

Term
A physician call the laboratory to verify a result of Mycobacterium tuberculosis, stating that the clinical history of the patient is not compatible with tuberculosis. On review of the patients culture , the smear was negative and the culture became positive at 5 weeks in the broth culture only. Additionally, it was determined  that another patients specimen that was processed the same day was 4+ AFB on smear and the culture was positive at 10 days for Mycobacterium tuberculosis. The lab should:
Definition

Perform molecular fingerprinting on both slides.if the molecular finger print is the same on both slides, the lab should review its processing procedures.

 

If the molecular fingerprint is the same, the smear neagtive culture sould be considered a false positive, and the laboratory should review its processing procedures

Term
Which of the following is considered a primary drug for the treatment of Mycobacterium Mycobacterium tuberculosis?
Definition

rifampin

The primary drugs for the treatment of Mycobacterium tuberculosis include ionizid, rifampin, pyrazinamide, and ethambutol.

Term
An unusual number of Mycobacterium gordonae have been isolated. The most likely source is:
Definition

Contamination by water organisms

 

Mycobacterium gordonae is widely distributed in soil and water., and is generally considered nonpathogenic.

Term
When grown in the dark, yellow to orange pigmentation of the colonies is usually demonstrated by
Definition

Mycobacterium scrofulacem

Mycobacterium scrofulacem is a scotochromogen.

Term
The Mycobacterium that produces a deep yellow or orange pigment both in dark and light are:
Definition

scotochromogens

Scotochromogens produce deep yellow or orange pigment when grown either light or darkness.

Term
Mycobacterium that produce pigment only after exposure to light are classified as:
Definition

photochromogens

Photochromogens produce nonpigmented colonies only when grown in darkness, but pigmented colonies after exposure to light.

Term
In a suspected case of Hansen disease (Leprosy), a presumptive diagnosis is established by:
Definition

detection of weakly acid-fast bacilli in infected tissue

Mycobacterium leprae cannot be cultured in vitro. A clinical diagmosis is made, supported by the presence of AFB in a biopsy specimen.

Term
The best medium for culture of Mycobacterium tuberculosis is:
Definition

Lowenstein jensen medium

 

Lowenstein jensen is an egg based medium used to isolate AFB. The other media are not used for the isolation of AFB

Term
A 27 year old scuba diver has an abrasion on his left thigh. A culture of this wound grew an acid-fast organism at 30*C. This isolate is most likely:
Definition

Mycobacterium marinum

Mycobacterium marinum causes infections as a result of trauma to the skin and exposure to contaminated fish tanks, or salt water. Its optimal growth temperature is 28-30*C

 

Term
A non-chromogen that grows best at 42*C and is highly resistant to antibiotics is:
Definition

Mycobacterium Xenopi

Mycobacterium Xenopi grows best at 42-45*C, and is not pigmented.

Term
Photochromogens produce pigment when:
Definition

exposed to light for 1 hour

Pigment production is controled by an oxygen-dependant, light-indicible enzyme in photochromogenic mycobacteria.

Term

An acid-fast bacillis recovered from an induced sputum had the following characteristics:

pigmentation: yellow in the dark, turning a deeper yellow-orange after 2 weeks of light exposure

Nitrate reduction: negative

Tween hydrolysis: positive at 5-10 days

urease: negative

Based on this information, the organism is most likely Mycobacterium:

Definition

gordonae

The characteristics given differentiate Mycobacterium gordonae from the other mycobacteria listed. M szulgai and flavescens are nitrate production positive, and M scrofulaceum is negative for Tween hydrolysis.

Term
Which of the following characteristics best distinguishes Mycobacterium scrofulaceum from Mycobacterium gordonae?
Definition

Tween hydrolysis

Tween hydrolysis differentiates Mycobacterium gordonae (Tween positive)  from M Scrofulaceum (Tween negative)

Term
Differentiation of Mycobacterium avium from Mycobacterium intracellulare can be accomplished by:
Definition

DNA probe

Mycobacterium avium  and M intracellular have the same biochemical pattern, but can be differentiated by the use of DNA probes.

Term
Which of the following species of Mycobacterium does not usually fluoresce on a fluorochrome stain?
Definition

Mycobacterium fortuitum

 

Rapidly growing mycobacteria such as Mycobacterium fortuitum may be <10% acid fast and may not stain with florochrome.

Term
A mycobacterial isolate that causes multiple skin nodules, grows at 30* and requires hemin for growth is Mycobacterium:
Definition

haemophilium

 Mycobacterium hemophilium grows best at 30*C , requires hemin of ferric ammonium citrate for growth, and causes subcutaneous lesions presenting as multiple skin nodules. 

Term
AFB smears of a lymph node biopsy from a child are positive At the end of 8 weeks, the AFB cultures are no growth. To enhance the possibility of recovery of the causitive organism, the technologist should?
Definition

incubate the cultures an additional 4 weeks.

Mycobacterium malmoense reqiures up to 12 weeks for growth. 

Term
The nitrate test for mycobacteria can be performed with a reagent impregnated paper strip or by use of standard reagents. In order to quality control the test properly, which of the following shaould be used for a positive control
Definition

Mycobacterium tuberculosis

Mycobacterium tuberculosis is the only mycobacterium listed that is nitrate reduction positive.

Term

**************Viruses and other Microorganisms**************

 

Virus transport medium containing penicillin, gentamycin and amphotericin is used to collect and transport specimens for virus culture because this medium:

Definition
Inhibits bacterial and fungal growth
Term
Which of the following indicates the presence of a viral infection in tissues smears or biopsys
Definition

Cytopathic effect

intra nuclear and intracytoplasmic inclusions

Term
Respiratory synctial virus is best isolated using a:
Definition
nasopharyngeal aspirate
Term
A urine specimen was submitted for isolation  of cytomegalovirus (CMV) , The urine was inoculated into human fibroblast tissue culture tubes. After 72 hours, no cytopathic  effect was observed in the culture tubes. The most appropriate course of action is to:
Definition

Incubate the culture tubes for 2-3 weeks longer.

(cytomegalo virus is a slow growing herpesvirus and may take up to 3 weeks to grow in conventional viral culture)

Term
The genus of virus associated with anogenital warts, cervical dysplasia and neoplasia is:
Definition

papilomavirus

Human papilimavirus (HPV) infects epithelial tissues throughout the body, including skin, larynx, and anogenital tissue. Persistant infection with oncogenic types of HPV and intergration of HPV DNA into the cellular genome is a pathway leading to HPV induced neoplasia , such as cervical cancer.

Term
Encephalitis is most commonly associated with which of the following viruses?
Definition

herpies simplex

Herpes simplex virus is the most common cause of fatal sporadic encephalitis in the United States 

Term
Colds and other acute respiratory diseases are most often associated with:
Definition
adenovirus
Term
The Epstein-barr virus is associated with which of the following?
Definition

Burkitt lymphoma

The classic clinical syndrome associated with Epstein-barr virus (EBV) infeection is infectious mononucleosis. However in immunocompromised patients, EBV is associated with posttransplant lymphoproliferative disorders, and maligncies such as Burkitt lymphoma

Term
Which organism fails to grow on artificial media or in cell cultues?
Definition

Treponemia pallidum,

Chlamydia trachomatis,Neisseria gonorrhoeae and herpes somplex virus can all be isolated in culture. Direct culture of Treponema pallidum on artificial media has not been acheived. Darkfield microscopy and serological techniques are used to diagnose T.pallidum infection.

Term
Darkfield microscopy is be used to visualize:
Definition

Treponemia pallidim

Darkfield microscopy can be performed to visualize Treponema palliidum in genital or skin lesions. Darkfield examination allows for the visualization of T pallidums typical morphology and motility.

Term
A wright stain on conjunctival smear from a neonate shows granular cytoplasmic perinuclear inclusions . This is the most indicative of:
Definition

Chlamydia trachomatis

The presence of typical intracytoplasmic inclusions are particularly useful in diagnosing  Clamydia tracomatis inclusion conjunctivitus. Multinucleated giant cells are seen  in cells infected with herpes simplex and varicella zoster virus. Cytomegalovirus produces large cells with intranuclear inclusions.

Term
Iodine staining of McCoy cells monolayer culture of a cervical swab reveals a large brown intercytoplasmic inclusion. What is the most likely infecting organism
Definition

Chlamydia trachomatis.

Iodine staining can be used to detect the glycogen rich cytoplasmic inclusions in Chlamydia trachomatis infected cells. These inclusions stain brown with iodine.

Term
Which compound, detected by Lugol iodine, is used in the non-immunologic detection of Chlamydia trachomatis in cell culture:
Definition

glycogen

Iodine staining can be used to detect the glycogen rich cytoplasmic inclusions in Chlamydia trachomatis infected cells. These inclusions stain brown with iodine.

Term
Microorganisms  resembling L-forms have been isolated from the blood of patients treated with antibiotics that:
Definition

interfere with cell wall synthesis

Bacterial L-forms are bacteria that lose their cell wall as a result as a result of therapy with cell wall active antibiotics, such as beta-lactam antibotics. Unlike mycplasma species, which permanently lack a cell wall, the lack of a cell wall in L-forms is a result of enviromental conditions. Once beta-lactam therapy is discontinued, an L form has the capability to grow a cell wall

Term
Relapsing fever in humans is caused by:
Definition

Borrelia recurentis

Relapsing fever is caused by Borrelia recurentis and is transmitted by the human body louse. Relapsing fever is characterized by the acute onset of high fever lasting 3-7 days, interspersed with periods of no fever, lasting days to weeks.

Term
Psittacosis is transmissable to man via contact with
Definition

birds

Chlamydia psittaci, the agent of psittacisis, is transmitted to humans via inhalation of nasal secretions as well as infected fecal and feather dust. 

Term
Chamydial infections have been implicated in
Definition

urethirtis and conjunctivitis

Chlamydia trachomatis is a well known cause of sexually transmitted infections. including urethritis and cervicitis, as well as inclusion conjunctivitis and pneumonia in neonates. It also causes trachoma and lymphogranulomas vernereum.

Term
Mycoplasmas differ from bacteria in that they
Definition

lack cell walls

Mycoplasma are smaller than other bacteria and lack a cell wall, instead they posess a trilaminar cell membrane. Because they lack a cell wall , they cannot be stained with gram stain. 

Term
A jaundiced 7 year old boy , with a history of playing in a pond in a rat infested area, has a urine specimen submitted for a direct darkfield examination, several spiral organisms are seen . Which of the following organisms would most likely be responsible for the patients condition?  
Definition

Leptospira interrogans

[image]

 Leptospira are spiral shaped organisms with hooked ends. They are ubiquitous in water (eg lakes, ponds) and assiciated with renal infections in animals, Leptospirosis is a zoonosis, and humans are usually infected via direct or indirect contact contact with the urine of infected animals (including rats). Between 5%-10% of patients with leptospirosis have the icteric form and develop jaundice, and may develop acute renal failure.

Term
A jaundiced 7 year old boy , with a history of playing in a pond in a rat infested area, has a urine specimen submitted for a direct darkfield examination, No organisms are seen in the specimen. Which medium should be inoculated in an attempt to isolate the suspected organism?
Definition

Fletcher semi-solid

The clinical syndrome described is most likely the icteric form of Leptospira interrogans. The most commonly used medium for culture is Fletcher semisolid agar. Cultures are incubated in the dark for up to 6 weeks at 28-30*C and examined weekly for by darkfield microspy.

Term
Which of the following is a growth requiremint for the isolation of Leptospira:
Definition

medium containing 10% serum plus fatty acids

.

Leptospiria cultures are incubated in the dark for up to 6 weeks in amibent air at 28-30*C, and examined weekly by darkfield microscopy. Fletcher semisolid agar contains peptone, bee extract and rabbit serum, which create an enriched medium to support the growth of leptospires.

Term
Blood cultures from a case of suspected leptospiremia should be drawn.
Definition

in the first 7 -10 days of infection.

 

Leptospiria organisms can be readily detected by culturing blood during the first week of illness. After this time the organisms disapprar from blood agar and are excreated from the urine for up to 1 month.

Term
What material should be used to prepare slides for direct smear examination for virus detection by special stains or FTA technique?
Definition

epithelial cell from the base of the lesion

 

Since viruses are intracellular organisms, the collection of cellular material is required to be able to demonstrate virus using stains or florescent techniques. Scraping of the base of a vesicle are required to collect cellular material. 

Term
A 29 year old man is seen for recurrence of a purulent uretheral discharge 10 days after the succesful treatment of cultures proven gonorrhea. The most likely etiology of his urethritis is:
Definition

Chlamydia trachomatis

Up to 1/3 of patients with Nessieria gonorrhoeae infection are also co-infected with Chlamydia trachomatis. Patients with identified infection with one organism are usually treated for both infections.

Term
Ureaplasma urelyticum are difficult to grow in the laboratory on routine media because of their requirement for:
Definition

sterols

Ureaplasma urelyticum, like other Mycoplasma, lack a cell wall and posess an extremely small genome. As a result, this organism has a limited biosynthetic capability and fastidious growth requirements. culture medium should contain serum (provides sterols), growth factors such as yeast extract and a metabolic substrate.

Term
A cell culture line used for the recovery of Chlamydia trachomatis from clinical specimens is
Definition

McCoy cells

McCoy cells in addition to buffalo green monkey kidney cells, are susceptible to infection with Chlamydia trachomatis, and are used routinely in the recovery of C trachomatis in culture.

Term
Rickettsiae infecting man multiply preferentially within which of the following cells?
Definition

endothelial

Rickettsiae species infect and multiply within vascular endothelial cells.

Term

****************Parasites*****************

 

Artifacts found in a stool specimen that can be confused with ova or cysts are:

Definition

pollen grains

Pollen grains are common artifacts in stool specimens submitted for ova and parasite examinations. Their appearance is similar to protozoan cysts.

Term

Polyvinyl alcohol used in the preparation of permanently stained smears of fecal material:

serves as an adheasive

Definition

serves as an adheasive

Polyvinyl alcohol is an adhesive and is used in the preparation of smears for stains such as trichrome.

Term
The method of choice to detect Acanthamoeba sp. from corneal ulcer scrapings is:
Definition

blood agar flooded with a 24 hour growth of E coli

The recommended technique for culturing Acanthamoeba is the use of non-nutriant agar seeded with a lawn of E coli. Specimens with suspected Acanthoameoba are inoculated onto a freshly inoculated lawn of E coli, incubated and observed for 7 days. Identification is based on the characteristics  patterns of locomotion and morphologic features of the trophic and cystic forms.

Term
Primary amoebic encephlitis may be caused by:
Definition

Naegleria foweleri

Naegleria foweleri is the etiologic agent  of primary amoebic encephalitis.

Term
A formed stool is recieved in the laboratory at 3 am for ova  and parasite exam . The night shift technologist is certian that the  workload will prevent examination of the specimen until 6 am. when the next shift arrives. The technologist should:
Definition

preserve the specimen in formalin until it can be examined

Formed stool is unlikely to contain trophozoites so direct examination  of the stool is not necessary. The stool should be preserved as soon as possible to preserve any cysts, ova or larvae that may be present in the specimen.

Term
A batch of trichrome stained slides for ova and parasite examination for ova and parasite examination contains numerous minute crystals, which totally obscure the microscopic field. Which of the following is the most appropriate  remedial action?
Definition

Change the iodine alcohol solution to obtain a strong tea-colored solution, restain

 

Incomplete removal of mercuric chloride may cause the smear to contain refractile crystals. Since the 70% ethanol-iodine solution removes the mercury, it should be changed at least weekly to maintain the strong tes color.

Term
The advantage of thick blood smears for malarial parasites is to:
Definition

improve detection of the organisms

The increased amount of blood placed on the slide of a thick smear for blood parasites improves the sensitivity of the smear. Thick smears should be preformed on all request for blood parasites.

Term
Multifocal brain lesion in AIDS patients is commonly caused by:
Definition

Toxoplasma gondii

The most common cause of ring enhansed brain lesions in a patient with HIV-AIDS is Toxoplasma gondii

Term
A 44 year old man was admitted to the hospital following a two week history of low grade fever, malaise and anorexia. Examination of a Gemsa stain revealed many intra erythrocytic parasites, Further history revealed frequent  camping trips near Mathas vineyard and Nantuckett Island  but no travel outside the continental United States. This parasite could easily be confused with
Definition

plasmodium falciprum

The patients history is suggestive of babesia infection. Babesia microti ring forms are similar to plasmodium falciprum. A travel history is helpful in determining the cause of infection.

Term

A patient is suspected of having amebic dysentary. Upon microscopic examination of a fresh fecal specimen for ova and parasites, the following data were obtained.

a trophazoite of 25 um

progressive , unidirectional crawl

evenly distributed peripherial chromatin

finely granular cytoplasm

This information probably indicates:

 

Definition

Entaomeba histolytica

The trophozoite of entamoeba histilytica ranges in size from 12-60 um, which is significantly larger than Endolimax nana. The nucleus of E histolytica displays evenly distributed peripheral chromotin unlike E coli, which has coarse peripheral chromatin and I butschii, which has none.

Term

Refer to the following image:

[image]

Trophozoites of the cyst shown above are likely to:

Definition

have slow, undefined motility

 

Entamoeba coli

Term

Refer to the following image:

[image]

Upon finding the above in a fecal concentration, the technologist should:

Definition

review the fecal concentration carefully for the presence of other microorganisms that may be pathogenic

(these are found in contamnated water) 

Entamoeba coli is a -pathogenic protozoan. its presence indicates the ingestion of fecally contaminated food or water and should lead to a closer review of the specimen  for pathogenic parasites or the collection of additional specimens.  

Term

Refer to the following image:

[image]

An inexperianced parisitology student may confuse the above organism with:

Definition

Entaomeba histolytica

(but they only have 4 nucleli)The cysts of Entamoeba coli and E histolytica may appear similar to the unexperianced technologist. E coli cysts are larger and contain more than 4 nuclei in each cyst.

Term

Refer to the following image:

[image]

This structure depicts:

Definition
a cyst of a nonpathogenic amoeba
Term

Refer to the following image:

[image]

the organism depicted is a:

Definition
flagellate:
Term

Refer to the following image:

[image]

A 24 year old woman, who just returned from vacationing in russia, became ill with steatorrheal diarhea, The above organism was found in her stool. The patient likely is suffering from:

Definition
giardiasis
Term
A liquid stool specimen is collected at 10:00 pm and brought to the laboratory for culture and ova and parasite examination. It s refrigerated until 10:00 am the next day, when the physician request that the techhnologist look for amoebic trophozoites. The best course of action would be to:
Definition
request a new specimen.
Term
Protozoan cysts are found in a wet mount of sediment from ethyl- acetate concentrated material.The cyst are without peripherial chromatin on the nuclear membrane. Each cyst has 4 nuclei, and each nucleus has a large karyosome, which appears as a refractile dot. These oval cysts are most likely:
Definition
Endolymax nana
Term
The term " internal autoinfection" is generally used in referring to infections with: 
Definition

Strongyloides sterocorlis

Strongolyodies rhabditifoem larve are capable of transforming into filiariform larve (infective form) larva in the intestine, and establishes an auto-infective cycle.

Term
The best method to demonstrate the ova of Enterbius vermicularis is:
Definition
cellophane tape preparation
Term
Proper collection of a sample for recovery of Enterobius vermicularis includes collecting:
Definition
a scoth tape preparation from the perianal region
Term
A fibrous skin nodule is removed from the back of a patient from central america. A microfliaria seen upon microscopic exam of the nodule is:
Definition

Onchocerca volvulus

Onchocerca volvulas is the only microfilaria that is deteccted in the skin snips of patients with raised skin nodules. The microfiliaria  of Whicheria, Bruglia and Loa loa are found in the blood.

Term

Refer to the following image:

[image]

The egg depicted above is most likely to be found in children suffering from:

Definition
perianal itching
Term

Refer to the following image:[image]

The specimen of choice for finding  the above parasite is:

Definition
scotch tape prepration
Term
The examination of human feces is no help in the detection of
Definition
Echinococcus granulosis
Term
The causitive agent of cystercercosis is
Definition
Tenia solium
Term
Organisms that can be eaisly identified to the species level from the ova in fecal specimens include:
Definition
Paragonimus westermani, Hymenolepis nana
Term
The scolex of taenia saginata has:
Definition
4 suckers
Term
When stool examination is negative , the preferred specimen for the diagnosis of paragonimiasis is:
Definition
sputum
Term
A stool specimen for ova and parasite examination contained numerous rhabditiform larvae. Which factor does not aid in the identification of larvae?
Definition
appearance of genital primordium
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