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Dermatology > Cross Strep Lecture > Flashcards

Cross Strep Lecture Flashcards

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1
Q

micro props of Strep

A

spherical GPCs in pairs, chains.
Cat-
hemolytic props important

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2
Q

GAS is

A

strep pyogenes

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3
Q

GBS is

A

strep agalactiae

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4
Q

Group D strep is

A

ENterococcus faecalis/faecium OR s bovis

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5
Q

GAS causes disease broadly by…

A

pyogenic inflamm
exotoxin
immunologic

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6
Q

b-hemolytic strep classified based on…

A

arranged in Lancefield groups based on Ag differences in C carbohydrate in CW

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7
Q

1st step in dx strep pharyngitis

A

rapid Ag test

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8
Q

strep pharyngitis cause

A

GAS

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9
Q

GAS pharyngitis dx

A

rapid strep Ag test, 10 min. spec, not sens. Throat swab. Ags extracted and reacted with Ab:latex –> agglut if GAS is present.

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10
Q

If rapid Ag test is negative but high suspicion of GAS pharyngitis, next step?

A

throat culture

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11
Q

what does alpha hemolysis look like?

A

green zone around colonies due to incomplete lysis

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12
Q

what does beta hemolysis look like?

A

clear zone around colonies due to complete RBC lysis

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13
Q

gamma hemolysis

A

no lysis

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14
Q

beta-hemolysis due to…

A

Streptolysin O: oxygen labile, UNDER agar surface

Streptolysin S: oxygen stable. ON agar surface

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15
Q

to test pt’s blood for past GAS pharyngitis, what Ab test for?

A

anti-streptolysin O

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16
Q

bact that are alpha hemolytic

A

viridans

s pneumo

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17
Q

bact that are beta hemolytic

A

GAS
GBS
GCS/GGS

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18
Q

bact that are non hemolytic

A

GDS. S bovis, enterococcus. some alpha hemolytic though

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19
Q

GAS virulence factors

A 
M prot
polysacch capsule
hyaluronidase
streptokinase
DNase
C5a peptidase
strep chemok protease
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20
Q

M protein

A

most important anti-phago of GAS. from outer cell surf, interferes w phagocyt. 80 serotypes.

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21
Q

polysaccharide capsule of GAS

A

hyaluronic acid. anti-phago, and no Ab formed against

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22
Q

hyaluronidase

A

GAS. degrades hyaluronic acid in subQ tissue. “spreading factor” helps GAS spread in cullulitis, etc

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23
Q

streptokinase

A

GAS. activates plasminogen –>plasmin. dissolves fibrin in clots, thrombi, emboli

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24
Q

DNase

A

GAS. degrades DNA in exudates/necrotic tissue. protects from NETS

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25
Q

C5a peptidase

A

cleaves C5a from complement, minimizes influx of neuts in early inf

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26
Q

strep chemok protease

A

prevents mig of neuts into site of inf by degrading IL-8

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27
Q

GAS pharyngitis can do WHAT if untx

A

otitis media, sinusitis, mastoiditis, meningitis, peritonsillar/retropharyngeal abscess
immune: rheumatic fever

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28
Q

GAS tx

A

do NOT delay! Oral penicillin, amox, orcephalexin 10 days

allergy? Azithromycin, clarithro, clinda.

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29
Q

GAS toxins

A

erythrogenic toxin
pyrogenic exotoxin A
exotoxin B

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30
Q

erythrogenic toxin

A

GAS. resp for rash of scarlet fever. SuperAg

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31
Q

pyrogenic exotoxin A

A

GAS. causes most cases of TSS. SuperAg–lots of cytok released

32
Q

exotoxin B

A

GAS. protease that rapidly destroys tissue, prod in large amoutns by “flesh eating” GAS strains –> nec fasciitis

33
Q

when does strep TSS occur

A

GAS infection, skin/ vagina/ pharynx. At site of minor trauma pts dev deep inf within 48-72 hrs, esp in soft tissue of an extremity

34
Q

strep TSS can progress to…

A

75% progress to necrotizing fasciitis

35
Q

sx of strep TSS

A

diffuse eryth, fever, chills, myalgia, n/v/d, hypothermia, hypoTN, AMS

36
Q

complications of strep TSS

A

DIC
AKI
ARDS
necrotizing fasciitis

37
Q

dx criteria of strep TSS

A

isolate GAS from normally sterile site (blood, CSF, biopsy) and hypoTN + other organs

38
Q

tx strep TSS

A

penicillin + clinda

39
Q

puerperal sepsis, endometritis

A

GAS
abdominal pain, hypoTN, fever
3.5% fatal

40
Q

post-strep GN cause

A

nephritogenic strains of GAS. happens post-SKIN inf. Ab:Ag complexes on GBM.

41
Q

post-strep GN sx

A

HTN, facial edema, LE edema, dark urine

42
Q

can post-strep GN be prevented?

A

probably not. most recover completely

43
Q

acute rheumatic fever cause

A

2 weeks after GAS pharyngitis, rheumatogenic strain. Ab against GAS prots cross react w host Ags in organs

44
Q

Jones Criteria for acute rheumatic fever dx

A 
Joints
Carditis
Nodules
Erythema marginatum
Sydenham chorea (neuro dis consisting of abrupt invol motion)
45
Q

help to acute rheumatic fever dx

A

ASO titer

46
Q

tx acute rheumatic fever

A

full course of antibiotic tx to eradicate any residual GAS.

THEN: prevent strep w prophylaxis in pts with hx of RF (penicillin monthly)

47
Q

brain abscess

A

viridans

peptostreptococcus

48
Q

peptostreptococcus

A

anaerobe
flora of gut, mouth, female genital tract
often in mixed anaerobic inf.
tx: penicillin

49
Q

endocarditis of s. bovis associated with….

A

colon carcinoma

50
Q

Janeway lesions

A

endocarditis. macular, nonpainful, eryth lesions on palms, soles

51
Q

Osler’s nodes

A

endocarditis. painful violaceous nodules in finger, toe pulm. subacute IE > acute

52
Q

Roth spots

A

endocarditis. exudative, edematous hemorrhagic lesions of retina

53
Q

endocarditis of s bovis

A

3 sets of blood cultures necessary to get a +

100% fatal!!

54
Q

Group D strep defining features

A

esculin-hydrolyzing if bile present

55
Q

types of GDS

A

enterococcus (faecalis/faecium) and s bovis

56
Q

entercoccus defining features

A

esculin-hydrolyzing in bile
grow in hypertonic saline
grow in bile
low virulence, capsule. enzymes. colon flora

57
Q

diseases of enterococcus

A

hosp-acq UTI, blood stream inf, endocarditis

58
Q

tx enterococcus

A

combo antibiotic: PCN/vanc, aminoglycoside. check susc

59
Q

vanco resistant entercoccus

A

more likely faeciUM. tx w linezolid or dapto

60
Q

s bovis props

A

hydrolyze esculin in presence of bile

not grow in hypertonic saline

61
Q

s bovis disease

A

endocarditis in pts w colon cancer.

62
Q

s bovis endocarditis tx

A

PCN, ceftriaxone, vanco

63
Q

VRE mech of resist

A

gene that encodes enz for D-lactate substit in peptidoglycan

64
Q

GBS micro

A

narrow zone b-hemolyssi
no esculin hydrolysis
bacitracin-R (opp to GAS)

65
Q

CAMP test

A

protein is produced that enhances hemolysis on sheep blood when + to beta-hemolysin of GAS

66
Q

virulence of GBS

A

inflamm resp. no toxins, enz. polysacch capsule is antiphago

67
Q

clinical GBS

A

genital tract of some women. Inf acq in utero or passage. babies: neonatal sepsis, meningitis, PNA
adults: invasive (septic arthritis, cellulitis, osteomyelitis.)

68
Q

risk factor of GBS

A

PROM >18 hr in colonized women, babies <37 wks, children whose moms lack Abs.
adults: DM, breast cancer

69
Q

GBS dx

A

grain stain
culture
rapid test for vaginal/rectal but not great. detectsDNA

70
Q

tx GBS

A

penicillin/ampicillin

vanc if allergies

71
Q

prevent GBS

A

screen all pregnant women 35-37 weeks. Admin PenG/Amp IV at time of delivery

72
Q

most common cause of subacute bact endocarditis?

A

viridans

73
Q

viridans diff lab props

A

alpha hemolytic
bile-lysis resist
optochin resistq

74
Q

viridans props

A

flora of mouth, colon. Enter blood post dental surgery or those w cavities

75
Q

strep mutans

A

viridans group. causes dental caries. makes polysacch in dental plaque

76
Q

pathogenesis of viridans

A

no enz, toxins. Can make glycocalyx (att to heart valve). Brain abscess, endocard, liver/abd abscess

77
Q

tx viridans

A

dep on susc
penicillin, ceftriaxone
for endocarditis with intermedsusc to PCN, + gentamycin

Dermatology (14 decks)

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