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Micro 2024 > Week 5 > Flashcards

Week 5 Flashcards

1
Q

All enterobacterales are

A
  1. Facultative Anaerobes
  2. GNB
  3. Oxidase negative
  4. Reduce nitrates to nitrites
  5. Fermenters
  6. Non-spore forming
  7. Grow on MAC
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2
Q

What four tube system is used to ID enterobacteriaceae

A
  • I = indole
  • M = MR
  • V = VP
  • C = citrate
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3
Q

E coli is

A

INDOLE: +
* MR +
* VP -
* CITRATE -

157:57 is NSF on SMAC while others do

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4
Q

Klebsiella pneumoniae is

A

INDOLE -
* MR -
* VP+
* CITRATE +

MUCOID LF
NON MOTILE
LOOSE LIDS BUT ATTACHED

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5
Q

Enterobacter aerogenes is

A

INDOLE -
* MR -
* VP +
* CITRATE +

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6
Q

Citrobacter freundii

A

INDOLE -
* MR +
* VP -
* CITRATE V (75%+)

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7
Q

Serratia marcescens *******

A

INDOLE -
* MR V (25%+)
* VP V (70%+)
* CITRATE +
*DNAse +

NLF OR LLF
may show red pigment

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8
Q

Providencia stuartii

A

INDOLE +
* MR +
* VP -
* CITRATE +

PPD +

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9
Q

Morganella morganii

A

INDOLE +
* MR+
* VP -
* CITRATE -

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10
Q

Difference between P Mirabilis and P vulgaris

SWARMING

A

M is indole neg and V is indole pos
Both are MR +
Both are VP -
M is citrate pos and V is citrate neg

WILL NOT SWARM ON MAC AND WILL NOT GROW ON CNA

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11
Q

Shigella sonnei

A

*INDOLE -
*MR +
*VP -
*CITRATE -

SUNNY D
serology is Shigella group D
Not positive for alot

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12
Q

Shigella flexneri

A

INDOLE V (29%+)
* MR +
* VP -
* CITRATE -

serology is Shigella group B

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13
Q

Yersinia enterocolitica

A

INDOLE V (50%+)
* MR +
* VP -
* CITRATE -
TRUE NLF not even on OPNG
MOTILITY non motile @ 35°C
* MOTILITY motile @ RT

UREA neg/wk+ @ 35°C
* UREA pos @ RT

Bullseye on CIN

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14
Q

Edwardsiella tarda

A

NDOLE +
* MR +
* VP -
* CITRATE -

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15
Q

which orgs are urea and PPF positive while all stool pathogens are negative for them

A
  • Proteus spp.
  • Morganella spp.
  • Providencia spp.

pink urea shows that it is not a stool pathogen

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16
Q

which orgs are Hydrogen Sulfide Positive

A
  • Citrobacter freundii - ONLY ONE LF
  • Edwardsiella tarda
  • Salmonella spp.
  • Proteus vulgaris
  • Proteus mirabilis
17
Q

which orgs are VP positive

A
  • Klebsiella spp.
  • Enterobacter spp.
  • Serratia spp
18
Q

which orgs are non motiles at 37

A

Shigella spp.
Klebsiella spp. (LF)
Yersinia spp. (motile at RT)

19
Q

which org is both a NLF at 24 hrs and LLF at 48 hrs

A

Shigella sonnei (onpg and ornithine post)

true for any org that is NF on MAC but ONPG positive

MALDI cant tell the difference between ecoli and shigella

20
Q

what are methods for AST testing

A

Vitek, Kirby
-AB groups depend on site of infection
-Enteric pathogens are not treated with antimicrobials but supportive therapy
-some Enterobacteriaceae are susceptible to broad spec cephalosporins
*ESBL
*SPICE

21
Q

What are extended spectrum beta lactamases

A

-plasmid meditated concern
-entrobacteriac can produce beta lactamase that is different from the one that causes penicillin and ampicillin resistance
-Class A is the infection control one - ESBL -extended Spectrum Beta Lactamase like Ecoli and Kleb
-these are able to resist cephalasporins, cephamycin, aztreonam, piperacillin

22
Q

What are class A esbls

A
  • are transferred on plasmids
    -this ability to transfer resistance is why it is of most concern because it can cause other infections
    -the gene is derived from TEM-1, SHV-1
    -inhibited by clavulanic acid which is a beta lactamase inhibitor
    -these are able to resist cephalasporins, cephamycin, aztreonam, piperacillin
    -Carbapenems are the drug of treatment
    -mostly e coli and kleb
23
Q

What are class C ESBLS

A
  • in some Enterobacteriaceae
  • Enzyme (cephalosporinase) hydrolyzes penicillins, cephlalosporins, monobactams , and cephamycins
    -Chromosomal –Intrinsic resistance; (may move to plasmids)
    -Induced by exposure to βeta-lactam drugs may look S in vitro but the treatment will fail once the pt is exposed to the beta lactam drug
    -found in SPICE organisms
24
Q

What is part of SPICE group **

A

Serratia spp
Providencia spp
Indole positive Proteus: Morganella, P. vulgaris
Citrobacter freundii
Enterobacter spp
(Hafnia has been added)

Chromosomally mediated natural resistance to beta lactams, cephalosporins, and cephamycins

25
What is the spice group
-first group of cephalosporin resistant organisms -have the inducible ampC Beta-lactamase which will look Sus in vitro but the treatment will fail after using beta lactamase AB -has a predictable resistance -resistant to B lactamase inhibitors and cephamycin's like cefoxitin -not part of infection control concern how will treatment work -avoid beta lactam antibiotics -must test susceptibility for Aminoglycosides, fluoroquinolones, SXT, carbapenems always reported as resistant to peni, cepha, b lactam inhibitor combos
26
how can we differentiate if it is a Spice or Class A ESBL
-know the spice orgs -check for 3rd gen cephalosporin -for Class A ESBL * For E. coli, P. mirabilis or Klebsiella sp., check the Ceftazidime result. This result is a screen for Class A ESBLs. * If it is S -> not a Class A ESBL * If it is R ->set up a PCT test to determine if it is a Class A ESBL -if the org is not a SPICE, ESBL or CPE Ceftazidime is used as a marker
27
what is the phenotypic confirmatory test
-testing to see if the class A B lactam can be inhibited by a b lactam inhibitor -Class A ESBLs are sensitive to Cefoxitin -There are five discs -use a standard disk diffusion at 35 C 16-18 hours -measure the drug alone against the drug + acid combo with a 5 mm difference the combo drug must be bigger for it to be ESBL positive ≥ 5mm difference between both or one pair of antibiotics + Cefoxitin S = Class A ESBL
28
What is Carbapenemase Producing Enterobacteriaceae (CPE)
-also known as Also called Carbapenem Resistant Enterobacteriaceae (CREs) or Carbapenem Producing Organisms (CPOs) -the resistance gene is transferable on plasmids -Resistant to carbapenems (e.g. ertapenem, meropenem, imipenem) -Resistant to all penicillins, cephalosporins, BL-inhibitory combinations - resistant to fluoroquinolones -hard to treat, causing poor patient outcomes like increase hospital stay -needs to be reported to public health -infection control issue -biggest risk factor is being in the hospital -NOT specific to enterobacteriaceae NDM - NewDehli -superbug **
29
What are Class A CPE
- Serine beta lactamases – hydrolyze all cephalosporins and carbapenems * KPC (Klebsiella pneumoniae carbapenemase), SME (Serratia marcescens)
29
What are Class B CPE
Metallo-beta lactamases: hydrolyze beta lactam rings using bound zinc ions * IMP (imipenemase), VIM (Verona integron-encoded MBL), NDM (New Delhi beta lactamase)
30
What are Class D CPE
Oxacillinases: characterized by their hydrolytic activity towards oxacillin * OXA (OXA-48 most common) * Shows weak activity against cephalosporins so may test S on Vitek (vs. Class A and B will test R)
31
What tests can be done for CPE production
-Modified CIM **** gold standard -ROSCO disks -CarbaNO -PCR
32
What is the Modified Carbapenem Inactivation Method (mCIM)
-make heavy suspension in saline -add meropenem disk and incubate for 2 hours at 35.If the organism has a carbapenemase enzyme, it will inactive the antibiotic in the disk. -after 2 hours streak a known meropenem Sensitive Ecoli for confluent growth on MHA -remove inactivated disk and put on plate with Sensitive E coli - incubate overnight -if the sensitive Ecoli grows on the disk the org has inactivated the meropenem meaning that it will have a CPE enzyme. However if the sensitive Ecoli still has a S zone size then there isnt a CPE enzyme in the organism
33
salmonella typhii
I- NEG M- POS NP-NEG CIT-NEG LITTLE BIT OF H2S IN THE MIDDLE OF THE TSI SEROLOGY Vi masks the o antigen
34
salmonella spp
I- NEG M- POS NP-NEG CIT-POS SEROLOGY O and H POSITIVE and Vi neg

Micro 2024 (13 decks)

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