Carbapenemases: Difference between revisions
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*Directed by susceptibility testing |
*Directed by susceptibility testing |
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| + | *See also [[Carbapenem-resistant organisms#Management|carbapenem-resistant organisms]] |
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| β | *For ESBLs and AmpCs, consider: |
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| β | **[[Ceftazidime-avibactam]] (not active against metallo-Ξ²-lactamases) |
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| β | **[[Meropenem-vaborbactam]] (limited activity against metallo-Ξ²-lactamases and oxacillinases) |
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| β | *For metallo-Ξ²-lactamases, consider: |
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| β | **[[Colistin]], though increasing resistance |
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| β | **[[Tigecycline]] |
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| β | **[[Fosfomycin]] |
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| β | **[[Aztreonam-avibactam]] |
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| β | **[[Cefiderocol]] |
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| β | **[[Eravacycline]] |
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| β | **[[Plazomicin]] |
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| β | *For carbapenem-resistant [[Pseudomonas aeruginosa]], consider: |
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| β | **[[Cefiderocol]] |
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| β | **[[Imipenem-relebactam]] |
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[[Category:Gram-negative bacilli]] |
[[Category:Gram-negative bacilli]] |
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Revision as of 08:15, 21 September 2020
Background
- Enzymes that hydrolyze carbapenems
- Includes members of all Ambler classes, which are in Bush-Jacoby classes 2df, 2f, 3a, and 3b
- Class A (2f): KPC, IMI
- Class B (3a and 3b): NDM, IMP, VIM
- Class C: AmpCs (occasionally weakly active against carbapenems)
- Class D (2df): 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
- Double disc diffusion (using Rosco discs)
- Class A: attenuated by boronic acid
- Class B: attenuated by diploconic acid
- Class C: attenuated by both cloxacillin and boronic acid
- Class D: not attenuated by boronic acid, diploconic acid, or cloxacillin
- Needs special discs, or PCR testing
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
Specific Carbapenemases
- IMI-1 confers resistance to carbapenems but not to cephalosporins1
Management
- Directed by susceptibility testing
- See also carbapenem-resistant organisms
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.
