Streptococci Flashcards Preview

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Flashcards in Streptococci Deck (19)
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1
Q

Strep morphology

A

Gram+ but in pairs or chains

2
Q

Beta hemolysis

A

Completely hemolyse RBC

3
Q

Alpha hemolysis

A

Partial hemolysis but looks cloudy, greenish around them

4
Q

Gamma hemolysis

A

No hemolysis!

5
Q

Group A

A

aka S pyogenes. Hides it’s F protein (binding) and M protein in a capsule, so it has to turn it off in order to bind. Spreading enzymes: hyaluronidase, DNases. Toxins: Strep pyrogenic exotoxin SPE, streptolysin O & S

6
Q

M protein

A

inhibits alternate complement pathway, antiphagocytic. Major virulence factor for S pyogenes

7
Q

Impetigo

A

Can be caused by strep and staph! Do test (hemolytic, morphology). Polysporin covers both.

8
Q

Erysipelas

A

More invasive, more deep than impetigo. Well demarcated edge to red area. Indicative of group A strep. Cellulitis less defined.

9
Q

Necrotizing fasciitis

A

Caused by S pyogenes. LTA and F protein bind fibronectin. Less defined edge to area. Delocalized pain from the red site visible, disproportionate amount of pain (burrows into fascia). Sometimes blisters on surface. Hyaluronidase and DNases aid spread quickly. Often associated with toxic shock.

10
Q

Cellulitis vs necrotizing fasciitis?

A

Depends on the bug and on your luck (immune system). If it remains localized it will be cellulitis. Can be caused by the same bug sometimes.

11
Q

Treatment of necrotizing fasciitis

A

Surgery, lots of antibiotics (penicillin and clindamycin), IgG to mop up M protein

12
Q

Strep throat vs a cold

A

Cold has runny nose typically

13
Q

Strep throat

A

Swollen uvula, red pinpoint lesions on palate, sometimes white spots on tonsils. But you can’t tell without a culture! Could still be viral.

14
Q

Scarlet fever

A

Can be secondary to strep infection. Sand paper rash and strawberry tongue. Results from the toxins (SPE). Treat to avoid acute rheumatic fever

15
Q

Actue rheumatic fever

A

Likely cross reactive T cells vs AB that react against self-antigens. Signs: arthritis, carditis, rash, subcutaneous nodules, chorea (involuntary movements like snake??). Can scar heart tissue. Treat strep throat within 7-10 days to avoid it.

16
Q

Group B strep

A

Aka Strep agalactiae. Still Beta hemolysis. Can cause damage to baby (meningitis, pneumonia, bacteremia)

17
Q

Viridans

A

Alpha hemolysis. Oral strep species

18
Q

Tx for viridians - categories

A

Antimicrobials (Chlorhexidine damages cell membrane and kills bacteria). Disruptors (Sodium lauryl sulfate – detergent which solubilizes plaque). Anti-adhesives (fluoride)

19
Q

Group D strep

A

Both gamma (non) hemolytic. Enterococci (endogenous, wimpy, cause UTIs and bacteremia in immunocompromised). Strep bovis: if in blood stream look for colon cancer (exam question!)