(Q9)

Name at least four genera that belong to the Enterobacteria that are lactose non-fermenters. 

• Proteus (mirabalis; vulgaris; penneri)
• Providencia (stuartii)

(Q9)

A Kligler Iron Agar slant shows a yello butt with blackish areas after growth in the incubator for 24 hours. What does this result indicate? 

Result indicates that glucose fermentation has occurred and ferris sulphide was produced. 

(Q9)

Which enteric bacterial species can cause pneumonia? 

Proteus spp.

(Q9)

How does the natural microbiota of the digestive sstem become established? Explain. 

(Q9)

Name a bacterial species that is a Gram negative rod, lactose negative, and does not belong to the Enterobacteriaceae. 

• Pseudomonas spp.
• Campylobacter spp. 

(Q8)

Name a human pathogen that belongs to the Apicomplexa. 

Plasmodium vivax

(Q8)

Name a human pathogen that is a flagellate. 

Trypanosomas cruzi

Trypanosomas bruceii

(Q8)

Name two modes of transmission for helminths in humans and five an example for each (name the species).

• ingestion - Taenieae saginata - beef tape worm
•  skin - Schistosoma

(Q8)

How are intestinal human protozoan and animal parasites detected in the laboratory? Explain. 

Intestinal human protozoa and animal parasites are detected by stool sample examination for eggs.

(Q7)

What is the difference between cystitis and pyelonephritis? 

Cystitis in an infection of the bladder and pyeloneprhitis is an infection in the kidneys. 

(Q7)

Name one Gram-positive and one Gram-negative bacterial species that commonl cause urinary tract infection. 

• Gram-positive
• Staphylococcus (epidermis; saprophyticus
• Enterococcus
• Gram-negative
• Escherichia coli
• Proteus
• Pseudomonas aeruginosa

(Q7)

How should a voided urine sampe be collected and handled to be useful in the diagnosis of UTI? 

Afre careful cleansing of rhe hands and genital area a urine sample should be taken mid-stream. Cup should not make contact with skin. Urine should be tested immediately, stored in the refrigerator, or treated with boric acid (if refrigeration is not possible), in order to prevent microbial growth. 

(Q7)

A pateint complains about a burning pain when urinating and the urge to frequently urinate. An investigation of a urine sample on Blood Agar (collected properly) revealed less than 1,000 cell/ml. Can you conclude that htis patient has no urinary tract infection? 

Although the number is not significant, the patient may still have an UTI as the pathogen resposible may not grow on Blood Agar.

(Q6)

What is the diference between an antimicrobial, an antibiotic and a semisynthetic drug? 

• antibiotic - living organisms that inhibit the growth of other living organisms
• semisynthetic - an antimicrobial that encompasses both living organism and a synthetic component
• antimicrobial - all antimicrobials, synthetic, semisynthetic, and antibiotics 

(Q6)

(T or F)

S. aureus can transfer resistance to Methicillin to Enterbacter faecalis. 

True

(Q6)

What does MIC and MBC stand for? 

• MIC - Minimum Inhibitory Concentration 
• MIB - Minimum Bactericidal Concentration

(Q6)

Briefly describe the MIC method. 

MIC make use of several wells containing either a broth or agar that conatin various concentrations of antimicrobial. A measured amount of a specific organism is inocculated into the edium and allowed to incubate. REsults are read according to amounf of growth. The one with the least concentration of antimicrobial showing no growht is th MIC.

(Q7)

Which culture media and conditions would you choose to culture a sample from a patient that might have contracted a sexually transmitted disease?

Would it be helpful to investigate a genital swab sample microscopically? 

It would be best to use an immunoassay test or a DNA test. A smear would possible show intracellular diplocci in a man which would be a presumptive diagnosis for N. gonnoerrhea, but not for a female.

(Q5)

How can Bacillus spp. be differentiated from Clostridium spp. in the laboratory? 

(Q5)

Case study 1: You are called about a 66 year old female long-term care resident who has had 5 episodes of loose diarrhea daily for the past 3 days. She now has a fever to 100.3°F, and is complainging of cramping lower abdominal pain. Microscopy of a stained ample of her stool found Gram-positive rods. Her history is significant for a recent UTI, caused by E. coli, for which she is currently on levofloxacin.

Should a urine sample be investigated again? Defend your answer.

It is not necesary to do another urine sample as the stool sample ant the fact that she is on antibiotics is indicative of antibiotic induced diarrhea (pseudomebranous colitis) caused by Clostridium difficile.

(Q5)

What species is responsible for gas gangrene?

What is the treatment for gas gangrene? 

Clostridium perfringens

(Q3)

(T or F)

Streptococcus pneumoniae possesses a capsule. 

True

(Q3)

Why does a culture of Bacillis subtilis have to be at least 

3-5 days old when you want to detect spores? In which growth phase are the organisms most likely in at this time? 

(Q3)

What kind of medium would you choose when you plan to detct the causative agent of a demal wound infection caused by bacteria? Why? 

(Q3)

What kind of medium would you choose when you want to detect the causative agent of severe diarrhea caused by bacteria? 

(Q2)

(T or F)

All prokaryotes have a peptidoglycan in the cell wall. 

False

Archaea do not have peptidoglican in their cell wall.

(Q2)

Name a selective and a differential medium and explain its application.

For what does it select?

What does it differentiate?

How does it achieve that? 

• PEA (phenylethyl alcohol agar): selective for Gram-positive bacteria. Contains phenylethyl alcohol which inhibits the growth of Gram-negative bacteria

• BAP (blood agar plate) differential for hemolytic organisms. Contains 5% defibrinated sheep blood.

(Q2)

Name a differential staining procedure and explain its application. What is differentiated and how? 

Spore stain: it differentiates the spores from the rest of teh cell by staining the vegetative cells so that the outside of the spore can be seen.