Strep Infections

Question 1

Beta-hemolytic organisms ____ lyse RBCs and include which 2 organisms?

Answer 1

Beta-hemolytic organisms completely lyse RBCs and include:

GAS = S. pyogenes

GBS = S. agalactiae

Question 2

alpha-hemolytic organisms ___ lyse RBCs and include which 2 organisms?

Answer 2

alpha-hemolytic organisms partially lyse RBCs and include:

S. pneumo

S. viridans

Question 3

gamma-hemolytic organisms ___ lyse RBCs and include which 2 organisms?

Answer 3

alpha-hemolytic organisms DON’T lyse RBCs and include:

S. enterococcus

S. bovis

Question 4

which 2 organisms are PYR positive?

Answer 4

S. pyogenes and Enterococcus

Question 5

M protein inhibits activation of ___ by binding ____ and protects {organism} against phagocytosis

Answer 5

M protein inhibits activation of complement by binding factor H and protects {S. pyogenes} against phagocytosis

Question 6

what layers are affected in erysipelas vs. cellulitis?

Answer 6

erysipelas = upper dermis only

cellulitis = deeper dermis and subcutaneous fat

Question 7

erysipelas is mainly caused by {organism}

Answer 7

erysipelas is mainly caused by {S. pyogenes}

Question 8

list the 4 criteria in Centor criteria for Strep pharyngitis

Answer 8

exudate

cervical adenopathy

fever history

lack of cough

Question 9

rheumatic fever follows only which infection?

Answer 9

ONLY pharyngitis (NOT skin infections)

Question 10

in a suspected patient with strep pharyngitis, check ____ which detects ____ antigen

Answer 10

in a suspected patient with strep pharyngitis, check rapid antigen detection test (RADT) which detects A-carbohydrate antigen

Question 11

what is Ludwig’s angina?

Answer 11

life-threatening infection of submandibular space, usually from dental infections with S. viridans

Question 12

the main virulence factor of H. influenzae is its _____ which protects against lysis by binding ____

Answer 12

the main virulence factor of H. influenzae is its polyribitol phosphate (PRP) capsule which protects against lysis by binding factor H

Question 13

type I necrotizing fasciitis is caused by ____

while

type II necrotizing fasciitis is caused by _____

Answer 13

type I necrotizing fasciitis is caused by polymicrobials

while

type II necrotizing fasciitis is caused by 1 organism (usually GAS)

Question 14

Strep toxic shock is caused by which protein strains?

Answer 14

M1 and M3

Question 15

which S. viridans groups are associated with dental infections and endocarditis?

Answer 15

Mitis group

Salivarius group

Mutans group

Question 16

which S. viridans group is associated with a brain of GI abscess?

Answer 16

Strep intermedius and Anginosus

Question 17

how do Enterococci species generate vancomycin resistance?

Answer 17

encodes peptidoglycan cell wall change: D-ala-D-ala –> D-ala D-Lac