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MSK (nlg) > Agents of bacterial skin infection > Flashcards

Agents of bacterial skin infection Flashcards

1
Q

manifestations from a distant infection site

A

toxin mediated

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2
Q

resident skin flora

A

mostly bacterial, includes staph epidermidis and p. acnes

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3
Q

transient skin flora

A

mostly staph aureus and strep pyogenes (group A)

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4
Q

spreading exogenous infection confined to epidermis

A

impetigo

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5
Q

spreading exogenous infection involving dermal lymphatics

A

erysipelas

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6
Q

spreading infection involving all the way down through subcutaneous layer

A

cellulitis

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7
Q

2 or more furuncles

A

carbuncle (abscess formation)

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8
Q

myonecrosis

A

muscle tissue death/infection

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9
Q

all streptococci are gram ___ and catalase ___

A

gram + and catalase -

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10
Q

all staphylococci are catalase ___

A

catalase + (distinguishes them from strep)

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11
Q

pyogenic cocci are obligate..?

A

obligate extracellular bacteria meaning they do not want to be inside cells

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12
Q

how do pyogenic cocci avoid being phagocytosed?

A

anti-phagocytic virulence factors

but sometimes cells have antibodies against these factors allowing uptake by PMNs

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13
Q

strep are classified by three things…

A
  1. hemolytic pattern (beta is clearing, alpha is partial)
  2. physiological traits and biochemical reactions
  3. antigenic composition (group A has A antigen in cell wall)
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14
Q

beta hemolytic strep

A

complete lysis of rbc around colony on blood agar

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15
Q

alpha hemolytic strep

A

partial hemolysis of rbc around colony on blood agar

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16
Q

gold standard detection method for group A strep?

A

culture

–strep is sensitive to bacitracin –> will be a clearing around bacitracin disc

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17
Q

group A strep

A

strep pyogenes

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18
Q

rapid looking for lancefield group A detection

A

strep test with great specificity but bad sensitivity

detects carbohydrate antigen that is part of cell wall murein layer, no virulence factor

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19
Q

major virulence factor in s pyogenes (group A)

A

M proteins

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20
Q

m protein

A

anti-phagocytic virulence factor in strep pyogenes

involved in binding to epidermis

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21
Q

why cant an antibody to hyaluronic acid be made against s pyogenes?

A

because humans have hyaluronic acid inour bodies so that would not be protective

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22
Q

components of streptococcal cell wall

A

capsule, m proteins, lipotechoic acid, phospholipid membrane

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23
Q

super antigens

A

stimulate excessive cytokine production –> lots of T cells

exotoxins involved in scarlett fever and toxic shock-like syndrome

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24
Q

extracellular virulence

A 
exotoxins/super antigens
streptolysin 0
DNAases
streptokinase
C5a peptidase
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25
Q

depolymerizes cell-free DNA in purulent lesions

A

DNAases

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26
Q

lyses blood clots helping bacteria spread

A

streptokinase

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27
Q

degrades complement component C5a that attracts PMNs

A

c5a peptidase

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28
Q

strawberry tongue, circum-oral pallor, desquamation

A

scarlet fever

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29
Q

purulent (pus) skin lesion

A

pyoderma

30
Q

four pyodermas caused by s pyogenes

A

impetigo
erysipelas
cellulitis
necrotizing fasciitis

31
Q

strep vs staph toxic shock syndrome

A

clinically the same except with strep patients are bacteremic(bacteria in blood) –>may have necrotizing fasciitis

32
Q

autoimmune cross reaction between anti-M antibodies and the heart tissue
group A strep

A

rheumatic fever

33
Q

renal injury due to deposition of antigen-antibody complexes on glomeruli

A

acute glomerulonephritis

34
Q

PANDAS syndrome

A

pediatric autoimmune neuropsychiatric disorder associated with group A strep

35
Q

5 criteria for PANDAS

A 
prescence of OCD or tic
pediatric onset
abrupt/episodic
GAS infections
neurologic abnormalities (hyper, tics, etc)
36
Q

how to treat pandas?

A

penicillin G or oral cephalisporins

if there is a co-infection with staph aureus, use penicillinase (will treat both)

37
Q

penicillinase

A

resistant antibiotic to treat both strep pyogenes and staph aureus at the same time

38
Q

what drug will treat both s pyogenes and s aureus simultaneously

A

penicillinase

39
Q

gram +, catalase +, coagulase -

A

staph epidermidis or staph saprophyticus

40
Q

gram +, catalase +, coagulase +

A

staph aureus

41
Q

white nonhemolytic colony morphology

A

staph epidermidis

42
Q

yellow beta hemolytic colony

A

staph aureus

43
Q

gram +, catalase -

A

streptococci

44
Q

catalase test

A

H2O2 plus bacteria

  • ->bubbling = catalase + (staph)
  • -> no bubbling = catalase - (strep)
45
Q

hallmark of staph skin infections?

A

presence of pus

46
Q

how to treat furuncle?

A

heat and or drainage

antibiotics if it invades subcutaneous layer

47
Q

hydradentic suppurativa

A

infection of sweat glands

48
Q

stye is what kind of infection and can progress to what?

A

folliculitis

can progress to cellulitis

49
Q

impetigo is usually due to?

A

group A strep

50
Q

binds fibronectin and induces shock

A

techoic acid

51
Q

converts fibrinogen to fibrin

A

coagulase

52
Q

hyaluronidase

A

acts on hyaluronic acids in CT facilitating dissemination through subcutaneous

53
Q

potent pore former, toxic to many cell types

A

alpha hemolysin

54
Q

also called spyngomyelinase C, kills cells via hydrolysis of membrane phospholipids

A

beta toxin

55
Q

cytolytic, nonspecific detergent like action

A

delta toxin

56
Q

poreforming toxins, lysis of neutrophils and macrophages

A

gamma toxin and panton-valentine leukocidin (PVL)

57
Q

staph intermedius

A

coagulase/staph zoonotic pathogen
common from dog bite or exposure
common oral, nasal, skin flora in healthy dogs

58
Q

food poisoning is caused by

A

staph enterotoxins

59
Q

TSST1

A

staph aureus induced toxic shock syndrome

60
Q

exfoliatin A/B cause…

A

staph aureus impetigo, Scalded skin syndrome, scarlet fever

61
Q

exfoliatin

A

a serine protease that splits desmosomes in granulosum

62
Q

major risk group for TSS

A

menstruating women
use ofcontraceptive devices
nasal surgery patients

63
Q

semi-synthetic penicillin

resistant to penicillinase

A

methicillin

64
Q

penicillinase-producing s aureus

A

generally plasmid encoded
transferred by conjuugation or transduction
treat with methicillin

65
Q

MRSA

A

due to mecA gene (encodes PBP2 - altered penicillin binding protein)
methicillin resistance

66
Q

what was developed to treat MRSA?

A

vancomycin - glycopeptide that binds to D-ala-D-ala residues of peptidoglycan precursors - stops chain

67
Q

VISA

A

vancomycin intermediate of s aureus

68
Q

VRSA

A

vancomycin resistant s aureus
acquisition of vanA gene
peptidoglycan precursor with D-ala-Dlactate terminus
hasnt spread as much as mrsa

69
Q

what causes UTI, endocarditis, infections of foreign devices, endophthalmitis, osteomyelitis?

A

s epidermidis

70
Q

biofilms

A

s epidermidis
irreversible adherence to device surfaces by extracellular polymers in a structural matrix
protects bacteria from antibiotics
nosocomial
detachment of bacteria can lead to sepsis

71
Q

nosocomial

A

arising in a hospital

72
Q

culprits of nosocomial skin infections

A

staph eureus
mRSA
acinetobacter baumanii
pseudomonas aeruginosa

MSK (nlg) (10 decks)

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