Streptococci Flashcards Preview

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Flashcards in Streptococci Deck (19):
1

Strep morphology

Gram+ but in pairs or chains

2

Beta hemolysis

Completely hemolyse RBC

3

Alpha hemolysis

Partial hemolysis but looks cloudy, greenish around them

4

Gamma hemolysis

No hemolysis!

5

Group 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

M protein

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

7

Impetigo

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

8

Erysipelas

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

9

Necrotizing fasciitis

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

Cellulitis vs necrotizing fasciitis?

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

Treatment of necrotizing fasciitis

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

12

Strep throat vs a cold

Cold has runny nose typically

13

Strep throat

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

Scarlet fever

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

15

Actue rheumatic fever

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

Group B strep

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

17

Viridans

Alpha hemolysis. Oral strep species

18

Tx for viridians - categories

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

19

Group D strep

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!)