Carbapenemases: Difference between revisions
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| − | == |
+ | ==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 |
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| − | === |
+ | ===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 35ºC 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 ≤15 mm (or pinpoint colonies up to 18 mm) |
| − | ** |
+ | **Negative if zone diameter is clear ≥19 mm |
| − | ** |
+ | **Indeterminate if clear diameter 16 to 18 mm, or pinpoint colonies ≥19 mm |
| − | * |
+ | *EDTA-modified carbapenem inactivation method (eCIM) |
| − | ** |
+ | **Only done if mCIM is positive, to test for metallo-β-lactamases |
| − | ** |
+ | **As above for mCIM, but adds EDTA to the tube |
| − | ** |
+ | **Positive for metallo-β-lactamase if zone diameter increases ≥5 mm from mCIM |
| − | *** |
+ | ***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 |
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| + | * '''Relebactam:''' active against KPC, but not OXA-48, VIM, GES, or MBLs |
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| + | * '''Tazobactam:''' active against [[Pseudomonas]], but limited activity against carbapenemases otherwise |
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| + | * '''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 09:54, 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 35ºC 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 ≤15 mm (or pinpoint colonies up to 18 mm)
- Negative if zone diameter is clear ≥19 mm
- Indeterminate if clear diameter 16 to 18 mm, or pinpoint colonies ≥19 mm
- EDTA-modified carbapenem inactivation method (eCIM)
- Only done if mCIM is positive, to test for metallo-β-lactamases
- As above for mCIM, but adds EDTA to the tube
- Positive for metallo-β-lactamase if zone diameter increases ≥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
- Relebactam: active against 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-β-lactamases)
- Meropenem-vaborbactam (limited activity against metallo-β-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.
