Carbapenemases: Difference between revisions
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***Ignore pinpoint colonies within any zones of inhibition in the eCIM |
***Ignore pinpoint colonies within any zones of inhibition in the eCIM |
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+ | ===Inhibitors=== |
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+ | *'''Avibactam:''' active against ESBLs, AmpCs, KPC, and OXA-48, but not MBLs and other OXAs |
| + | **Only inhibitor with some activity against class D (OXAs) |
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| β | * '''Relebactam:''' active against KPC, but not OXA-48, VIM, GES, or MBLs |
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| β | * |
+ | *'''Relebactam:''' active against ESBLs, AmpCs, and KPC, but not OXA-48, VIM, GES, or MBLs |
| β | * |
+ | *'''Tazobactam:''' active against [[Pseudomonas]], but limited activity against carbapenemases otherwise |
| + | *'''Vaborbactam:''' active against KPC, but limited activity against MBLs and OXA-48, [[Pseudomonas]], or [[Acinetobacter]] |
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==Management== |
==Management== |
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Revision as of 10:04, 12 September 2020
Background
- Enzymes that hydrolyze carbapenems
- Includes members of most Ambler classes
- Class A: KPC
- Class B: NDM, IMI, VIM
- Class C: AmpCs
- Class D: OXA-48
Identification
- Screening is done by identifying isolates with decreased susceptibility to one or more carbapenems
- Testing "not susceptible" to ertapenem is the most sensitive indicator
- Typically also resistant to third-generation cephalosporins, as well, with the exception of SME in Serratia marcescens and IMI
- A modified Hodge test can confirm the presence of a carbapenemase, but is no longer routinely recommended
- Modified carbapenem inactivation method (mCIM)
- Place meropenem disc in a suspension of the test isolate, and incubate at 35ΒΊC for 4 hours
- Remove disc, squeezing out excess fluid, and place on a lawn of susceptible Escherichia coli
- Positive for carbapenemase if zone diameter is clear β€15 mm (or pinpoint colonies up to 18 mm)
- Negative if zone diameter is clear β₯19 mm
- Indeterminate if clear diameter 16 to 18 mm, or pinpoint colonies β₯19 mm
- EDTA-modified carbapenem inactivation method (eCIM)
- Only done if mCIM is positive, to test for metallo-Ξ²-lactamases
- As above for mCIM, but adds EDTA to the tube
- Positive for metallo-Ξ²-lactamase if zone diameter increases β₯5 mm from mCIM
- Ignore pinpoint colonies within any zones of inhibition in the eCIM
Inhibitors
- Avibactam: active against ESBLs, AmpCs, KPC, and OXA-48, but not MBLs and other OXAs
- Only inhibitor with some activity against class D (OXAs)
- Relebactam: active against ESBLs, AmpCs, and KPC, but not OXA-48, VIM, GES, or MBLs
- Tazobactam: active against Pseudomonas, but limited activity against carbapenemases otherwise
- Vaborbactam: active against KPC, but limited activity against MBLs and OXA-48, Pseudomonas, or Acinetobacter
Management
- Ceftazidime-avibactam (not active against metallo-Ξ²-lactamases)
- Meropenem-vaborbactam (limited activity against metallo-Ξ²-lactamases and oxacillinases)
- Colistin
- Tigecycline
References
- ^ Jeanette W. P. Teo, My-Van La, Prabha Krishnan, Brenda Ang, Roland Jureen, Raymond T. P. Lin. Enterobacter cloacae producing an uncommon class A carbapenemase, IMI-1, from Singapore. Journal of Medical Microbiology. 2013;62(7):1086-1088. doi:10.1099/jmm.0.053363-0.
