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Determinative Bacteriology
Family Streptococcaceae Genus Streptococcus
54
Microbiology
Post-Graduate
09/17/2010

Additional Microbiology Flashcards

 


 

Cards

Term
Group B Streptococci
Definition

 

GBS, commonly colonize the lower gastrointestinal tract and vaginal epithelium of healthy adults, but they remain a potentially devastating pathogen to susceptible infants. 
Because the newborn is deficient in host defenses, ie, phagocytes, complement and specific antibody; therefore an environment exists for potential problems
The first strains of GBS were studied by Lancefield, these strains were isolated from cows with mastitis, and was a concern mainly in the dairy industry.
First report of GBS in humans appeared in 1938.  In the 1960’s reports of hemolytic GBS among newborns.  In the 1970’s GBS eclipsed E. coli as the leading cause of newborn sepsis.  Today colonization of GBS in mother a risk factor for neonates.

 

Term
Group B Streptococcus: 
Definition

 

Gram positive cocci, Example species: Streptococcus agalactiae
Beta hemolytic
BacitracinR
SXTR
Hippurate hydrolysis +
CAMP +
Growth in 6.5 % NaCl, variable
Bile esculin
PYR -

 

Term
Bacitracin Susceptibility
Definition

 

Disk test performed on Blood agar medium.
Look for a zone or no zone around the disk.
Group B streptococci, are resistant, no zone around the disk.

 

Term
Sulfamethoxazole-Trimethoprim
SXT test
Definition

 

This test distinguishes groups A and B streptococci from other streptococci.
Both Groups A and B are resistant to SXT.
Disk test done on agar surface.

 

Term
Hippurate hydrolysis
Definition

 

Group B streptococci are able to hydrolyze hippurate to glycine and benzoic acid.
Broth test contains hippurate, incubated with cells, centrifuge cells, collect supernatant, add ferric chloride, ppt means benzoate present.  Or add ninhydrin to check for glycine, deep blue color.

 

Term
Identification of Group B Streptococcus
Definition

 

Camp Test
Use a beta hemolytic S. aureus 25923.
Group B Streptococci, produce a protein called “CAMP Factor”, that interacts with the beta hemolysin produced and secreted by S. aureus to cause enhanced hemolysis.  This appears as an arrowhead.
Presumptive for Group B streptococci.

 

Term
Bile Esculin Test
Definition

 

Accomplished in Bile Esculin medium.
Tests the ability of certain streptococci to grow in the presence of 1-4% Bile salts and hydrolyze esculin to esculetin.  Which in the presence of Fe++ forms a black complex.
Group B streptococci are negative.

 

Term

Growth in 6.5 % NaCl

(GBS)

Definition

 

Group B streptococci are variable.

 

Term
Identification tests for Group B streptococci
Definition

 

All of the previous including growth in Lim broth
Optochin(ethyl hydrocupreine hydrochloride) susceptibility, a disk test done on blood agar.  However must measure the zones of inhibition.  A zone of 14 mm or greater around the 6 mm disk indicates susceptibilty.

Group B streptococci are resistant.

 

Term
Lim Broth
Definition

 

Todd Hewitt Broth supplemented with 10μg/ml nalidixic acid, 15μg/ml colistin, 10mg/ml yeast extract. 
Todd Hewitt broth:  use 30g/liter of
Beef heart, 500g
Neopeptone, 20g
Dextrose, 2g
Sodium chloride, 2g
Disodium phosphate, 0.4g
Sodium carbonate, 2.5g

 

Term
Pyrrolidonyl arylamidase(pyr) test
Definition

 

Broth containing pyrrolidonyl-naphthylamide is incubated with the bacterium for 4 hrs.  If pyr is hydrolyzed, free naphthylamide is detected with a diazo dye, red color.
Group B is negative.

 

Term
Virulence Factors Group B,
β-hemolytic streptococci
Definition

 

Capsule

sialic acid 
C5a peptidase
β hemolysin
Lipoteichoic acid
C antigen
Cell surface penicillin binding protein
Hyaluronic acid lyase

 

Term
GBS Capsule
Definition

 

Capsule:  (CPS) 9 types, the polysaccharide capsular antigens are designated Ia, Ib, II, III, IV, V, VI, VII, VIII.  These capsules are composed of glucose, galactose, N-acetylglucosamine, sialic acid.  The types are comprised of differing arrangements of these carbohydrates.  Most predominant infections are the result of types: Ia, Ib, II, III and V. 

 

Term
GBS Sialic acid
Definition

 

The presence of sialic acid on GBS creates a surface that does not activate the alternative complement pathway, therefore a virulence factor on GBS

 

Term
GBS C5a peptidase
Definition

 

C5a peptidase: C5a is a complement component, that is produced by alveolar epithelial cells, and acts as an attractant for inflammatory cells.  Therefore the C5a peptidase cleaves the C5a at the C terminus and interfers with C5a mediated neutrophil chemotaxis.  

 

Term

GBS β hemolysin

Definition

 

β hemolysin seen as a virulence factor in pulmonary infections.  This creates pores in pulmonary alveolar epithelial cells, suggesting a role in neonatal infections.

 

Term
GBS Lipoteichoic acid
Definition

 

Lipoteichoic acid:  facilitates adherence as a first step in infection.  

 

Term
GBS C antigen
Definition

 

C antigen:  cell surface protein that mediates the internalization of these organisms in cervical endothelial cells.

 

Term

GBS Cell surface penicillin binding protein

 
Definition

 

Cell surface penicillin binding protein, enables streptococcal cells to resist intracellular killing by phagocytic cells. 

 

Term
GBS Hyaluronic acid lyase
Definition

 

Hyaluronic acid lyase:  may help to spread infection by breakdown of this component in placental tissues, fetal tissue and amniotic fluids.  

 

Term
Clinical significance of Group B
β hemolytic streptococci
Definition

 

Major cause of disease in neonatal and perinatal (period shortly before and after birth) periods.  Females, have the organism in their rectum and vagina, 10-35%.  Up to 60% of females will carry the organism intermittently.  Colonization of the vagina may reflect contamination from the rectum. 
The presence of Group B strep in the vagina of the mother at the time of birth can lead to infection of the neonate.  

 

Term
Pathogenesis of Group B streptococci
Definition

 

Meningitis:  Group B streptococci are the leading cause of neonatal meningitis in the US during the first 4 months of life.

Neonatal sepsis, two forms: Maternal carriage is a risk factor.  Maternal antibodies to CPS of GBS is low in these females.

Early onset, occurs in utero or within 5 days of birth. Mortality rate 50%, 2.9 cases/1,000 births
Late onset, occurs 10 days to 4 months.  Mortality rate of 20%. Possibly spread via breast feeding from GBS infected mastitis in mothers. 

 

Term
Group B streptococci General Info
Definition

 

Normal habitat: pharynx, vagina and stool.

Example species:  Streptococcus agalactiae, is a beta hemolytic streptococcus, first recognized in 1938, as a cause of “childbed fever”. 
In the 1970’s leading cause of neonatal meningitis as well as postpartum endometritis
1990’s 3-4 cases per 100,000 cases of invasive S.agalactiae, in non pregnant adults.

 

Term
GBS disease in nonpregnant adults
Definition

 

Most common infections caused by GBS in adults are skin, soft tissue and bone infections.  Usually these infections are complications of chronic diabetes.  Patients with indwelling catheters are at high risk for GBS bacteremia.  Pneumonia is a severe form of GBS disease with high mortality

 

Term
Treatment for Group B streptococcal disease
Definition

 

Penicillin G plus an aminoglycoside.
Heavily colonized mother’s are treated intrapartum to prevent colonization of their newborns.  

 

Term
GBS vaccines
Definition

 

Early clinical trials gave mixed results, vaccines based on specific capsules from strains need to be made more immunogenic.  Conjugate vaccines, (polysaccharide-protein) seem to offer the best protection.  

 

Term
Group C streptococci
Definition

 

Gram positive cocci
Lancefield grouping
Beta or alpha hemolysis
Normal habitat: Pharynx, vagina and skin
Pathogenesis
Example species: S. equi and S. dysgalactiae.
S. dysgalactiae subsp. equisimilis most human isolate, recovered from carriers and those within exudative pharynigitis and tonsillitis.
S. equi causes a respiratory infection in horses called “strangles”.  High fever, mucopurulent nasal discharge and lymph node abscesses.    

 

Term
Identification of Group C streptococci
Definition

 

Beta hemolysis
Bacitracin variable
SXTS
CAMP negative
Hippurate negative
PYR negative
Bile esculin negative
Growth in 6.5 % NaCl negative
OptochinR

 

Term
Group D streptococci
Definition

 

All posses a common group D cell wall antigen
They grow in the presence of Bile esculin
Two groups:
Enterococci
Non-enterococci

The term “enterococcus”, dates to the late 1800’s.  The enterococci were given genus status in 1984.

 

Term
Enterococci
Definition

 

Various hemolytic reactions
SXTR
Growth in 6.5% NaCl and 40% bile salts
Growth at 10°C and 45°C
Hippurate variable
Hydrolysis of pyrrolidonyl arylamidase
Growth on KF agar.
Normal habitat: large bowel
PathogensisUTI,endocarditis
Ex species:   E. faecalis, E. facium and   E.durans

 

Term
Enterococci general info
Definition

 

These organisms are normal residents of the GI and biliary tracts and lower numbers of the vagina and urethra.  Found in human feces 105 to 107 /g.
Most common cause of nosocomial UTI and wound infections, rarely cause pneumonia and meningitis.  Involved with 15-20% endocarditis.
Third most common cause of nosocomial bacteremias
Resistant to penicillin, cephalosporins and acquisition of high level vancomycin resistance, makes them dangerous in serious superinfections in patients receiving antibiotics. 
VDE, vancomycin-dependent enterococci, first described in 1994, enterococci that only grow in the presence of vancomycin.  A problem with long term usage.  

 

Term
Infections caused by enterococci
Definition

 

E. faecalis and E. faecium, account for 95% of all enterococci infections.  They are now the leading cause of surgical site infections.  Diseases caused by these strains is compounded by their intrinsic and acquired antibiotic resistance. 

 

Term
Virulence factors, enterococci
Definition

 

Some strains of E. faecalis produce:
Cytolysin/hemolysin, acts on RBC’s.
Aggregation substance, plasmid encoded protein that promotes clumping.
Extracellular surface protein, helps the microbe evade antibodies. 
Lipoteichoic acid, constitute the group D Ag, induces interferon production.
Coccolysin, an extracellular metalloendopeptidase which inactivates a vasoactive peptide.  

 

Term
Unusual molecules produced by enterococci
Definition

 

Phermones:  Plasmid encoded, small peptide that promotes conjugation between enterococci.
Bacteriocin AS-48:  a wide spectrum antimicrobial peptide produced by these bacteria.  

 

Term
Non-enterococci
Definition

 

Group D streptococci
Failure to grow in 6.5% NaCl
SXTS
PYR negative
Various hemolysis reactions
Example species:  S.bovis, S. equinus
S. bovis, 2 biotypes observed, “1” is mannitol +, “2” is mannitol -.  Group 2 were human isolates, Group 1 were cattle isolates.

 

Term
Group F streptococci
Definition

 

Anginosus group
Gram positive cocci
Normal habitat: oral cavity, throat
Demonstrate all 3 types of hemolysis.
Pathogenesis:  sinus infections, deep tissue abscesses, endocarditis.
Ex species: S. anginosus
Same identification profile as the Group C

 

Term
Group G streptococci
Definition

 

Gram positive cocci
Normal habitat:  mouth, throat, G.I. tract, and skin flora.
Many types of infections
Beta hemolytic

 

Term
Group K streptococci
Definition

 

Ex species:  S.salivarius

 

Term
Lancefield Group “NONE” streptococci
Definition

 

Gram positive cocci
Alpha hemolytic
Negative for hippurate, growth in 6.5% NaCl, and CAMP
Ex species:  S. pneumoniae
Leading cause of community acquired pneumonia
Penicillin sensitive
ID in lab:  Quellung Reaction, Bile Salts and Optochin susceptibility

 

Term
Virulence factors Streptococcus pneumoniae
Definition

 

Polysaccharide capsule (remember S and R studies by Griffith in mice, proving DNA)
Teichoic acids and lipoteichoic acids
Pneumolysin
Autolysin
Neuraminidase enzymes
Hyaluronidase
IgA proteases
PspA (pneumococcal surface protein)

 

Term
S. pnuemoniae Polysaccharide capsules
Definition

 

Polysaccharide capsules:  90 types, 23 account for bacteremia / meningitis.  Long polymers of repeating units of 2-7 monosaccharides different impacts on the host.

 

Term
S. pneumoniae Teichoic acids
Definition

 

Teichoic acids:  cell wall associated attached to the peptidoglycan.

 

Term
S. pneumoniae Lipoteichoic acids
Definition

 

Lipoteichoic acids:  linked to the membrane, repeating units of glucose, NAG, ribitol 5-P.

 

Term
S. pneumoniae Pneumolysin
Definition
Pneumolysin:  53,000 daltons, cytotoxic protein, interacts with cholesterol in cell membranes, it also inhibits bactericidal activity of phagocytic cells.  
Term
S. pneumoniae Autolysin
Definition

 

Autolysin:  separates daughter cells after cell division, also breaks down bacteria to help spread pneumolysin and α hemolysin.  

 

Term
S. pneumoniae Neuraminidase
Definition

 

Neuraminidase:  cleave terminal sialic acid from cell surfaces to expose NAG-galactose moieties that mediate bacterial cell attachment.  

 

Term
S. pneumoniae Hyaluronidase
Definition

 

Hyaluronidase:  facilitates spread of the organism.  

 

Term
S. pneumonia IgA1 proteases
Definition

 

IgA1 proteases:  inactivates sIgA to facilitate colonization.  

 

Term

 

S. pneumoniae PspA   
 

 

Definition

 

PspA:  surface protein, function unknown.  

 

Term
Pneumococcal vaccines
Definition

 

2 vaccines produced: pure polysaccharide vaccines and polysaccharide-protein conjugate vaccines. 
Comprised of 23 capsular serotypes. 
Given to:  people 65 yrs or older, persons 2-64 yrs who have chronic illness, those with sickle cell, people living in high risk environments “nursing homes”, immuno compromised individuals.  

 

Term
Clinical significance
Definition

 

S. pneumoniae, major cause of community acquired bacterial pneumonia.
The microbe may be harbored in the upper respiratory tract of 5-10% of adults, with higher carriage rates in closed populations.
Most serious infections occur in adults > 65 yrs of age, and infants < 3 yrs of age.  Mortality rate approaches 70% among treated patients older than 70.
In the host the microbe gains access to the alveolar spaces by aspiration and may result in lobar pneumonia.
Approximately 500,000 cases/yr in the US.      

 

Term
Viridans streptococci
Definition

 

Heterogeneous group of streptococci, “oral streptococci”, grouped on the basis of 16s rRNA, since they do not contain a “C” carbohydrate. 
Alpha or non hemolytic on sheep’s blood.
Members of this group are harbored in the nose and throat of >95% of humans, and with the exception of S. mutans, do not cause a disease in the “normal” host.
Clinically causes 30-40% of all subacute bacterial endocarditis, usually have preexisting valve problems. S.oralis, S.mitis, S. mutans, S. salivaris.  Usually from dental manipulation in patients with these problems.
S. mutans, have glucosyltranferases, that hydrolyze sucrose in the diet, connect the glucose moieties and form dental plaque.  They produce a large amount of acid, role in dental carries.

 

Term
Identification of the Viridans streptococci
Definition

Hemolysis alpha or none

Bacitracin variable
SXTS
CAMP negative
Hippurate hydrolysis variable
PYR negative
Bile esculin variable
Growth in 6.5% NaCl negative
OptochinR

 

Term
Anaerobic streptococci
Definition

 

Genus Peptostreptococcus, most significant pathogen in the group.  Normal flora of the mouth, intestinal tract and vagina.  

 

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