Keeping "CRE" out

Last week was officially “CRE” (carbapenem-resistant Enterobacteriaceae) week, and I encourage anyone who hasn’t done so to read Eli’s excellent posts about the entirely predictable emergence and spread of these bad bugs. Before this crisis disappears down the media memory hole, it is worth mentioning one additional line of defense against CRE that is not up to the challenge: our clinical microbiology laboratories. This is particularly concerning when the new recommendations made by the CDC in response to CRE require additional laboratory support: (1) confirmatory testing and determination of the carbapenem resistance mechanism for CRE, and (2) rectal screening cultures of all patients admitted to U.S. hospitals who were hospitalized outside the U.S. in the prior 6 months.

The CDC provides a phenotypic method for CRE screening, and there are several other published methods (including commercial screening agars), but these approaches don’t provide clinically relevant turnaround times, nor do they tell us which mechanism is at work (e.g. KPC, NDM, VIM, IMP, etc.). Some referral centers use home-brew PCR tests for the most common carbapenemase in the U.S. (KPC), and there are commercial assays being developed that utilize real-time multiplex PCR to detect several enzymes at once, but these tests aren’t available to most labs. So if your hospital lab does find a bug that looks like a possible CRE (after 24-72 hours!), it can perform the Hodge Test (which isn’t great for emerging carbapenemases), send the bug out to a reference lab….and wait for the result.

I completely understand why the CDC has recommended new screening questions + rectal swabbing as part of CRE response. However, trying to keep these organisms from entering our hospitals and long-term care facilities using screening questions and rectal swabs is like depending upon a poorly built levee to hold back floodwaters. 

Dramatic advances in hand hygiene, environmental disinfection, and antimicrobial stewardship, on the other hand, would be the prevention equivalent of moving out of the floodplain to higher ground. Allow me to dream, please!


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