6. Multi-Drug Resistant Organisms Flashcards Preview

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Flashcards in 6. Multi-Drug Resistant Organisms Deck (36):
1

Combination therapy to treat Enterococcus infections?

Ampicillin-sulbactam
Amoxicillin-clavulanate
Piperacillin-tazobactam

2

What 2 types organisms is the CarbaNP test for?

Enterobacteriaceae
Pseudomonas aeruginosa

that are I or R to 1+ carbapenem

3

ESBL confirmation test

Phenotypic confirmatory test

4

Often used against MRSA, but rapid development of resistance => not recommended for monotherapy

Rifampin

5

Most common carbapenemase?

Class A (KPC)

6

Test that predicts mecA-mediated resistance in S. aureus

30 ug cefoxitin disc

7

Methicillin resistant Staphylococcus aureus are strains that have MICs to oxacillin = __ ug/mL.

4

8

Difference between G+ and G- B-lactamases?

G+ = exoenzymes secreted by organism

G- = concentrated in periplasmic space; not secreted

9

When is inducible B-lactamase resistance in staph tested for?

whenever a staph tests "S" to penicillin

10

Next step after staph tests 'S' for pencillin?

Test for inducible B-lactamase

11

3rd gen = R
1st gen = S
What does this suggest?

ESBL

12

Patient screening for MRSA - appropriate anatomical sites?

- Anterior nares (nostrisl)
- Axillae (armpits)
- Wounds, drain sites

13

Penicillin zone edge test 'sharp zone edge' interpretation?

'Fuzzy zone dge'?

Sharp = B-lactamase production POS

Fuzzy = NEG

14

MRSA strains are _____________: have both “S” and “R” subpopulations

hetero-resistant

15

Purpose of 4% salt MHA plate

MRSA strains grow well at higher [salt] => pushes expression of mecA gene

16

Used in the cefinase test for induced hyper beta lactamase production

1 ug oxacillin disc

17

2 types of MRSA screening media?

MSAO - mannitol salt agar w/ oxacillin
- mannitol fermenters = possible MRSA = yellow
- CoNS = white/pink

Chromogenic agars

18

4 penicillinase-labile penicillins

Penicillin
Amoxicillin
Ampicillin
Piperacillin

19

Patient screening for VRE - appropriate anatomical sites?

- Stool, perineum/rectum
- Neck, groin (neonates)

Less common = urine, open wounds, drain sites

20

Used in the screen test for oxacillin resistance in staph

MH agar w/ 4% NaCl and 6 ug/mL oxacillin

21

S. aureus strains that are R to oxacillin but S to amoxicillin/clavulanic acid

BORSA

22

Organism that shows some resistance to oxacillin (usually "I" MICs) are called...?

BORSA

23

New subclass of cephalosporin w/ anti-MRSA activity

Ceftaroline

24

3 types of VRE screening media?

Chromagar plates

BEAV - brown-black colonies w/ dark halo

VRE selective broth - look for evidence of black/grey growth, subculture to agar

25

4 common B-lactamsae inhibitor combo drugs

Amoxicillin/clavulanic acid

Ticaricillin/clavulanic acid

Piperacillin/tazobactam

Ampicillin/sulbactam

26

Why should isolates of enterococci from sterile sites have nitrocefin beta-lactamase test done as well as routine KB susceptibility testing?

Resistance to ampicillin and penicillin due to B-lactamases cannot reliably be predicted by routine KB or MIC methods

27

MRSA treatment alternatives - particularly if community-acquired and non-invasive

Tetracyclines, SXT

28

3 penicillinase-stable (resistant to B-lactamase) penicillins

Oxacillin
Cloxacillin
Methicillin
Nafcillin

29

Detection of inducible AmpC B-lactamases?

Cefoxitin = primary screen

30

How is low level vancomycin resistance in Enterococci detected?

BHI w/ 6ug/mL vancomycin (part of routine AST for all enterococci)

31

3 class B carbapenemases

NDM-1
IMP-type
VIM

32

Test that must be done for all BORSA isolates?

B-lactamase test

33

Beta lactamase test common uses what antimicrobial?

Nitrocefin

34

Purpose of mCIM vs eCIM?

mCIM - detect carbapenemases

eCIM - differentiates metallo-B-lactamases from serine carbapenemases (only interpreted if mCIM POS)

35

Confirmation of inducible AmpC B-lactamases?

E-test AmpC strip => uses cefotetan (less sensitive than cefoxitin)

Cefoxitin-cloxacillin double-disk synergy (CC-DDS)
- cloxacillin inhibits AmpC B-lactamases

36

The 4 drugs that may be used to screen for ESBL producers?

- Ceftazidime
- Cefotaxime
- Azthreonam
- Ceftriaxone