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Mercy CLS 2: Microbiology > 2. Staphylococcus > Flashcards

2. Staphylococcus Flashcards

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Biology 101 flashcards
1
Q

Micrococcus habitat

A

Environment, food

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2
Q

Rothia habitat

A

Mouth, URT

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3
Q

Staph relationship to O2

A

Facultative anaerobes

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4
Q

Staph tolerates —% salt

A

10

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5
Q

Differentiates Staph from Strep

A

Catalase

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6
Q

Function of protein A
Who has it?

A

SAUR

Binds the Fc of IgG. Prevents opsonization and phagocytosis.

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7
Q

2 functions of catalase

A

Breaks down toxic end-products of glucose metabolism (H2O2)

Breaks down the myeloperoxidase system so organism can survive within WBC

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8
Q

function of hyaluronidase and fibrinolysin

A

Breaks down connective tissue. Allows organism to move through the tissues.

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9
Q

Superantigens

A

Stimulate T cells to produce a large burst of cytokines leading to an overwhelming inflammatory response and multi-disease and shock syndrome

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10
Q

B-lactams work by binding to…

A

penicillin binding proteins (PBP)

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11
Q

B-lactamase produced by —% of Staph now

A

90

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12
Q

CA-MRSA is likely to produce this virulence factor

A

Panton-Valentine Leukocidin (PVL)

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13
Q

Clinical effects of PVL

A

Causes severe skin infections and necrotizing pneumonia. Often fatal within 72 hours.

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14
Q

2 types of coagulase and their respective test methods

A

Bound/clumping factor—Slide coag test

Free—Tube coag test

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15
Q

———-, present in plasma, reacts with bound coagulase, ——- forms and coats the cocci causing them to…..

A

Fibrinogen, present in plasma, reacts with bound coagulase, fibrin forms and coats the cocci causing them to clump together

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16
Q

Saline control for slide coag test check for——

A

autoagglutination

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17
Q

negative —- coag must be confirmed with —- coag

A

slide
tube

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18
Q

—–% of SAUR may be false negative by slide coag test

A

10-15

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19
Q

SNA that produces clumping factor but not free/extracellular coagulase

Slide pos (false), tube neg.

A

SLUG

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20
Q

Free coagulase activates a ———– which is modified into a ———– molecule. The molecule then reacts with fibrinogen to produce a fibrin clot.

A

Free coagulase activates a plasma coagulase reacting factor (CFR) which is modified into a thrombin like (TL) molecule. The TL molecule then reacts with fibrinogen to produce a fibrin clot

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21
Q

Rare strains of SAUR can be tube coag negative because…

A

Naturally produce little/no coagulase

Produce staphylokinase, dissolving clot

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22
Q

SNA that may be slide neg, tube pos.

A

SINT

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23
Q

Staph latex detects…

A

bound coagulase
protein A

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24
Q

Staph latex beads are coated with…

A

human plasma/fibrinogen
IgG to protein A

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25
Q

Staph latex false Pos organisms

A

SSAP
MLUT

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26
Q

Staph latex false neg

A

MRSA
capsule - masks clumping factor, protein A

Requires more expensive test, including Ab against capsule.

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27
Q

Commercial ID systems ideal for Staph…

A

from sterile specimens like blood

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28
Q

molecular methods of ID most useful for…

A

epidemiology studies
outbreak investigations

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29
Q

MSA salt conc.

A

7.5%

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30
Q

About ——-% of healthy individuals are colonized with SAUR in the nose and/or perianal region

A

25-35

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31
Q

clinical sign of direct SAUR invasion

A

pyogenic

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32
Q

blood cultures for osteomyelitis positive in —-% of cases

A

50

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33
Q

toxin associated with impetigo

A

exfoliatin

34
Q

—% of impetigo cases due to SAUR

A

90

35
Q

susceptibility testing done on all Staph

A

oxacillin/methicillin
vancomycin

36
Q

most common SNA

A

SEPI

37
Q

Most labs do not ID down to SNA species, except when…

A

From normally sterile site

From artifical device

38
Q

1 positive SNA blood bottle per 6 =

2+ positive SNA bottles per 6 =

A

contaminant

pathogen

39
Q

Fluorescent bright white gamma colonies from urine

A

SSAP

40
Q

SSAP is coag —– and staph latex ——

A

negative
possibly weak positive (unsure why)

41
Q

organism we use novobiocin testing for

intrinsically resistant

A

SSAP

42
Q

SSAP zone of novobiocin inhibition should be ≤ —- mm

A

12

43
Q

modified oxidase test distinguishes….

A

Micrococcus
blue positive

44
Q

modified oxidase tests for organism’s ability to make ——–

A

cytochrome c oxidases

45
Q

No valid method for susceptibility testing

A

SSAP
MLUT

46
Q

Rothia has no growth in —% salt

A

5%

47
Q

S. aureus of dogs

A

SINT

48
Q

Could falsely report as MRSA due to tube coag positive and PPB2a latex positive

A

SINT

49
Q

Double zone of beta hemolysis

A

SINT

50
Q

Can break through MSA or chromogenic agar

A

SINT

51
Q

PYR necessary to distinguish SAUR (neg) from…

A

SINT
SLUG

52
Q

aggressive, destructive skin and soft tissue disease

A

SLUG

53
Q

SNA sensitive to all antibiotics, which can distinguish it from SAUR

A

SLUG

54
Q

Slide coag pos, latex pos, but susceptible to all antibiotics

A

SLUG

55
Q

function of PBP

A

produce enzymes essential in producing and maintaining the peptidoglycan layer for the gram-positive cell wall

56
Q

B-lactamase-resistant drugs

A

Methicillin, nafcillin, and oxacillin

57
Q

how did MRSA “learn” to resist the B-lactamase-resistant drugs?

A

mecA
makes new PBP2a

58
Q

SNA with potential to be methicillin R

A

SINT

59
Q

synergetic drugs #1
function
examples

A

irreversible inhibition of beta-lactamase

Sulbactam, clavulanic acid and tazobactam

60
Q

Ampicillin/sulbactam (Unasyn)
Amoxicillin/clavulinic acid (Augmentin)
Piperacillin/tazobactam (Zosyn)

A

synergistic drugs

61
Q

Daptomycin, linezolid, tigecycline, minocycline, quinupristin/dalfopristin and telavancin

A

new drugs held in reserve for MDR strains—even R to vanc.

62
Q

Vancomycin (glycopeptide) intermediate (VISA/GISA) cause

A

unusually thick cell wall that blocks vancomycin, which is very large in size

63
Q

VISA morphology

A

small colonies

64
Q

how did VRSA arise?

A

MRSA obtained the vanA gene for vancomycin resistance from VRE

65
Q

—- cases of VRSA in US so far

A

16

66
Q

linezolid, daptomycin, telavancin, ceftaroline, tigecycline, minocycline or quinupristin-dalfopristin

A

used to tx VRSA

67
Q

R to erythromycin, S to clindamycin indicates organism does NOT have….

but it COULD have…

A

The constitutive erm gene (Always turned on); Resistance due to efflux (Always turned on)

Inducible erm

68
Q

E/CC test for inducible erm

A

D test

69
Q

now used to predict resistance due to mecA gene

better inducer than oxicillin

A

cefoxitin

70
Q

Weak/false positive for catalase
Enterococcus

A

pseudocatalase

71
Q

Tube coag false negative cause

A

Fibrinolysin

72
Q

staph latex can only be used to test which organisms?

A

Cat + GPCs

73
Q

indicator in MSA

A

phenol red

74
Q

present in chromogenic agar to select for MRSA

A

cefoxitin

75
Q

CO2 creates false ——- results on chromogenic agar

A

negative

76
Q

Rothia vs Staph

A

Rothia does not grow in 5% salt

77
Q

SNA gives POS tube coagulase

A

SINT

78
Q

SNA gives POS slide coagulase

A

SLUG

79
Q

SSAP and Novobiocin

A

Resistant

80
Q

Distinguish SAUR from SINT and SLUG

A

PYR is neg for SAUR

81
Q

Bile POS, salt NEG

A

SGAL

Mercy CLS 2: Microbiology (16 decks)

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