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RC Test 4 > B4.068 - Staph Aureus a Pyogenic Model > Flashcards

B4.068 - Staph Aureus a Pyogenic Model Flashcards

1
Q

common gram negative pus forming bacteria

A

Neisseria E. Coli Pseudomonas

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2
Q

common gram positive pus forming bacteria

A

Strep pyogens staph aureus

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3
Q

what is suppuration

A

the formation of pus

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4
Q

what is pus

A

a mixture of living and dead neutrophils, bacteria and cellular debris

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5
Q

where does pus usually form

A

in an area of persistent infection

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6
Q

what is an abcess

A

a circumscribed collection of pus associated with infection

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7
Q

does an abscess respond to antibodies or antibiotics

A

no, not accessible

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8
Q

one way to get rid of abscesses

A

drain it

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9
Q

how do abscesses form

A

activation of macrophages and other cells of the innate immune system chemotactic factors produced by resident cells - acute phase response activation of adaptive immunity and Th17 acute inflammation

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10
Q

what cells are involved in acute inflammation

A

infiltration of neutrophils production of lysosomal enzymes

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11
Q

describe how the shape of an abscess forms

A

the inflammatory area is contained within a thick walled fibrin capsule the host thinks it has contained an invading organism

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12
Q

what is a complication of abscesses

A

if the abscess happens to be in or near a vital organ or tissue it can often have serious consequences

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13
Q

describe staph a.

A

gram + coccus grows in irregular grape like clusters non motile, non spore forming and catalase and coagulase positive

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14
Q

what is staph a resistant to

A

high temp high salt (haloduric) drying

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15
Q

describe how staph a looks

A

colonies are golden and strongly beta hemolytic on blood agar

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16
Q

describe staph a on mannitol salt agar

A

produces a yellow color with phenol red indicator

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17
Q

what is ClfB

A

clumping factor B

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18
Q

what is IsdA

A

iron regulated surface determinant

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19
Q

what populations have higher rates of staph colonization

A

health care workiers diabetics patients on dialysis

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20
Q

main site of staph a colonization

A

anterior nares

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21
Q

other staph a colonization sites

A

axilla, rectum, perineum vaginal carriage rate is 10% in premenopausal women, rate higher during menses

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22
Q

how can staph spread inside the body

A

from abscesses heatogenously

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23
Q

how does staph. a spread hematogenously

A

due to proteolytic enzymes

can result in pneumonia, bone and joint infection and heart valve infection

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24
Q
A

janeway lesions seen in endocarditis

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25
Q
A

osler nodes seen in endocarditis

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26
Q
A

roth spots seen in endocarditis

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27
Q

how does endocarditis initially present

A

fever and malaise

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28
Q

mortality rate of staph a septicemia

A

80%

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29
Q

mortality rate of staph a TSS

A

3-5%

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30
Q

TSS criteria for diagnosis

A

Fever > 38.9

Rash

hypotension

nausea, vomiting, diarrhea

myalgia, high Cr

conjuctival hyperemia

blood urea high

high bilirubin, transaminases

thrombocytopenia

disorentation

31
Q

what is a concern for a neutropenic cancer patietn with a central venous line

A

sepsis due to s. aureus

32
Q

most frequent cause of septicemia following a surgical procedure

A

staph aureas

33
Q

most common place to contract MRSA

A

hospital

34
Q

common manifestations of staph

A

skin

wound

scalded skin syndrome

35
Q

common staph skin infections

A

folliculitis

furuncles, carbuncles

impetigo

36
Q

what is ritter disease

A

scalded skin syndrome

37
Q
A

folliculitis

a tender pustule involving a hair follicle

38
Q
A

furuncle

small abscess that exudes purulent material from a single opening

39
Q
A

carbuncle

an aggregate of furuncles with several openings

40
Q

typical findings of septic arthritis

A

warmth

erythema

tenderness of the joint with symptoms and fever

infection almost always unilateral

41
Q

what is osteomyelitis

A

bone infection indicated by fever and bony tenderness or limp

42
Q

catheter associated infections are often due to what

A

staph epidermis

43
Q

urinary tract infections in sexually active young firls often due to

A

staph saprophyticus

44
Q

staph saprophyticus symptoms

A

often seen in sexually active young girls

dysuria

pyuria

45
Q

does staph aureus have a capsule

A

yes, inhibits phagocytosis

46
Q

what is protein A

A

seen in staph a

binds to the H chain of antibody and can inhibit antibody opsonization preventing phagocytosis. can activate the classical C pathway

47
Q

is s. aureus coagulase + or -

A

positive

this means it was the ability to coagulate plasma and form a fibrin barrier around infectious loci.

48
Q

what is staphylokinase

A

something staph aureus can relase that breaks down fibrin clots, note it is also coagulase + so it has the ability to make clots and break them down

49
Q

what is PVL

A

panton valentine leukocidin

a phage derived exotoxin that causes leukocyte destruction and necrosis. espeicially in the skin and lungs

50
Q

what are exfoliatin toxins

A

seen in staph aureus

consists of ETA or ETB

result in scalded skin syndrome

51
Q

features of scalded skin syndrome

A

fever

erythema

blisters (bullae) which eventually rupture adn leave a red base.

positive nikoskys signs

52
Q

what is bullous impetigo

A

a localized form of SSSS

unlike disseminated SSSS the bulae are culture positive

nikoskys sign absent

occurs primarily in infants and young children

highly communicable

53
Q

what are enterotoxins A-E adn G-I

A

responsible for types of common food poisoning

staph aureus

supeantigens that stimulate ceratin T cells by binding to the TCR Vbeta chain

stimulate production of cytokines like IFN gamma and TNF causing inflammation of the tissues

54
Q
A

antigen on left

superantigen on right

55
Q

what are enterotoxins and what do they do

A

often localized to the gut but can be fatal if systemic

often occur from skin of food handlers

cause vomiting and watery diarrhea 2-6 hours after ingestion

symptoms usually self limited

56
Q

should you give antibiotics for enterotoxin mediated staph food poisoning

A

no it wont help, the toxin is there its not the bug causing the problem. its self limited

57
Q

what is TSS

A

caused by a superantigen

first described in children

frequently associated with tampons

associated with strains that produced TSST-1

mimics endotoxic shock

58
Q

what strains other than ones that produce TSST-1 can cause toxic shock

A

ones that produce enterotoxin B, C can cause 50% of cases of non mestrual TSS

pathophys mimics endotoxic shock

59
Q

case definition of TSS

A

fever

diffuse macular erythema

may mimic sunburn rash

hypotension

involvement of organ systems
GI - emesis or diarrhea

renal dysfunction

hematologic - low platelets

muscular - severe myalgia

hepatic - elevated liver enzymes

NS - diorientation

60
Q

diagnosis fo staph aureus

A

culturs with susceptibility testing

blood culture may be positive when results from other cultures are negative

61
Q

most purulent infections caused by what

A

staph aureus unless proven otherwise

62
Q

most important defense agaistn s. aureus

A

neutrophils

63
Q

what are important immunological factors for defense against staph aureus

A

opsonization and antibody and Cā€™ involved

64
Q

what is not a major factor in staph aureus defense

A

MAC

65
Q

what adaptive components of the immune system are importatn in staph aureus defense

A

T cells - Th17

IL-1

66
Q

what is the most important innate immune system componet for staph aureus

A

TLR-2 - peptidoglycan

67
Q

women who experiecen TSS have what

A

lower antibody titers againts TSST-1

68
Q

coagulase negative staph types

A

staph epidermidis most common

lack many virulence factors and often require a means of entry

69
Q

staph epidermidis can cause problems with what

A

artifical heart valves, strep more common for natural valves

also catheters

70
Q

what indicates a positive coagulase test

A

formation of fibrin clot or gel

71
Q

why does staph enterotoxin B cause observed clinical effects

A

it activates certain T cells to produce cytokines

72
Q

staph superantigens stimulate what

A

T cells

73
Q

endotoxins stimulate what part of the immune system

A

macrophages

74
Q
A

left - spider bite

right - MRSA

differentiate using a culture

RC Test 4 (10 decks)

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