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11 Cards in this Set

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Streptococci

gram

catalase

categorized by

-surface structure of group A strep is.. and leads to..
Gram positive cocci in chains or pairs
C. Catalase negative
D. Categorized by hemolysis pattern on sheep blood agar Alpha: partial or greening hemolysis Beta: complete hemolysis gamma or nonhemolytic: no hemolysis
E. Beta strep also categorized by Lancefield groups as A,B,C,D,F,G. This grouping is created by cell wall carbohydrates that are antigenic and precipitate with specific antisera
F. Surface structure of Group A streptococci can be very antigenic; this leads to the nonsuppurative complications seen
II. Group A strep (Streptococcuspyogenes (pus-producing)

-why is it called group A
-causes what kind of infection
-hemolysis type
-hemolysins?
-what toxins make the external effects of strep A?
-has lancefield antigen A (c carbohydrate)
. Causes purulent infections
B. Beta hemolytic: 2 hemolysins, (this is what destroys the RBCs)Streptolysin S and Streptolysin O
C. Pyrogenic exotoxins A, B, C... produce external effects including the
rash of scarlet fever
Others: streptokinase, hyaluronidase, dexoxyribonucleases, C5 alpha
peptidase
what type of toxin?

causes what?
The M protein is?
Produces a number of exotoxins and enzymes that cause tissue destruction
and/or toxic shock like symptoms
: the major virulence factor; variable from strain to strain
and allows subtyping; helps resist phagocytosis; also weak point bc B cells make antibodies against M
protein confer type specific resistance
Diseases
1.
complications
2.
3.
4.
and 2 delayed antibody mediated diseases
5
6
-RF and GN are .... infections
with what symptoms?
1. Pharyngitis and tonsillitis: diagnose with strep screens and throat culture; complications include otitis, abscesses, rheumatic fever (RF), glomerulonephritis (GN)
2. Skin infections: impetigo (crusty mouth thing around mouth), erysipelas, cellulitis, fasciitis, post-op wound infections, GN (NOT RF)
3. Scarlet fever: Pharyngitis + strawberry tongue, rash
4. Toxic shock-like syndrome: shock, renal failure, rash, respiratory failure





5. RF: carditis, polyarthritis, chorea, erythema marginatum (rash with red margin spreading from center),
subcutaneous nodules + arthralgia, fever, high ESR, EKG changes, evidence of Group A strep
6. GN: presents one week after infection edema, hypertension, hematuria, proteinuria

-nonsuppurative complications
Diagnosis
Rapid strep screen on throats: specific, not sensitive
2. Culture on blood agar
3. ASO, antiDNAse B, other titers may help demonstrate recent infection
III Group B Streptococci (Streptococcus agalactiae
-B hemo
Frequently colonizes female genital tract and gi tract
B. Important cause of neonatal sepsis and meningitis (1-3/1000 live
births, mortality 30-60%)
C. Post-surgical gyn infections
D. Infections in the elderly: uti, bacteremia, pneumonia, skin, wound
infections
E. Automatic screening of all women at 35-37 weeks gestation is recommended
IV. Group C,D,F,G Streptococci
Group C,D,F,G Streptococci

-causes what type of infection
-RF GN?
-which ones are food bourne types of what?
-associated with colon cancer
-Which one has bacteremia
-group F is called... Is part of what group and causes what?
Can cause purulent infections like Group A
B. No clear association with RF or GN
C. Food-borne outbreaks of pharyngitis with C and G
D. Bacteremia with Group D (Streptococcus bovis) associated with colon
cancer E. Group F includes Streptococcus milleri, usually part of the viridans group
that is associated with aggressive tissue abscesses
Streptococcus pneumoniae
-appear as
-hemolysis
-virulence
-colonize what and associated with what
Usually appear as diplococci
B. Alpha hemolytic
C. Virulence related to capsule (numerical typing scheme)
D. Commonly colonize upper respiratory tract
E. Colonization/infection associated with recent viral uri, airway obstruction,
immunosuppression, splenectomy, alcoholism F.
Diseases:
pneumonia, otitis (in kids), sinusitis, meningitis (in adults), bacteremia,
Viridans group Streptococci
-hemolysis
-confused with what? yet what is the difference?
D. Diseases:
Alpha or nonhemolytic
B. Some have lancefield antigens and may be confused with Beta-hemolytic Groups of strep. The difference is that these organisms all have very small colonies on agar media while the real Lancefield group organisms have large colonies
-endocarditis, dental infections, abcesses
Enterococcus
-hemolysis
-diseases
-significant thing
B. May be non, alpha, or beta hemolytic
C. Common part of gi tract flora
D. Diseases: bacteremia, uti, wound and soft tissue infections, endocarditis
E. Important as nosocomial pathogens
F. VRE: vancomycin resistant enterococci, also resistant to all other available antibiotics, associated with nosocomial outbreaks