Monday, March 30, 2009

New CDC Guidance for Carbapenem-Resistant Enterobacteriaceae

The CDC just issued new guidance for labs and infection control programs to help detect and control carbapenem-resistant Enterobacteriaceae (CRE).

You can read this guidance for yourself, but the quick and dirty summary is: (1) micro labs should follow the latest CLSI guidelines to detect carbapenemases, which means doing a modified Hodge test on all isolates with elevated carbapenem MICs; (2) all patients infected or colonized with CRE should be placed in contact precautions; and (3) all hospitals should review up to a year of lab data for unrecognized CRE, and perform point prevalence surveys in high risk units if CRE if found. When CRE is detected, epidemiologically-linked patients should be screened for CRE—with continued screening until there is no evidence for cross-transmission. Additional measures are consistent with those already recommended in the CDC’s guidelines for control of multidrug-resistant organisms.

I’m of two minds about this new CDC guidance….on the one hand, I welcome any clear recommendations for control of multiply drug resistant gram negative rods (MDR-GNRs). On the other hand, CRE is only one of many MDR-GNRs, and the screening method currently recommended by the CDC is CRE-specific and is of uncertain sensitivity in clinical practice—many hospitals are also battling garden-variety ESBLs, AmpC-producers, MDR-Acinetobacter and Pseudomonas, and others. There is already evidence that screening for MDR-Acinetobacter (even with multi-site sampling), is poorly sensitive. So a negative screen can be falsely reassuring—it may not exclude CRE carriage, it doesn’t exclude carriage of other MDROs, and it represents only one point in time (and unfortunately, patients don’t become MDRO colonized at 3 or 7 day intervals for our convenience). Remember when we used to think that swabbing a nostril and plating to solid media would detect almost all MRSA carriers?

As resistant organisms accumulate, with increasingly complex patterns of resistance and colonization, we will need to revisit our assumption that actively seeking carriers of the “bad bug du jour” (and placing those carriers in contact precautions) is the right solution. Are we prepared to perform multi-site sampling tests (that are of questionable sensitivity) to assess for asymptomatic carriage of MRSA, VRE, ESBLs, CRE, MDR-Acinetobacter/ Pseudomonas, C. difficile, and on and on? It might be better to take our cue from the standard precautions philosophy, and assume that all patients harbor pathogens that can be transmitted in our hospitals. Take a uniform approach to all patients, including standard precautions (including better hand hygiene!), bundled approaches to prevention of device-associated infections, liberal use of chlorhexidine (bathing, dressings, oral care), and selective use of barriers as outlined by Kathy Kirkland—and reserve active surveillance for outbreak settings.

Addendum: The last paragraph of my post above isn’t meant to imply that I disagree with this new CDC guidance….this important guidance was issued in response to what is really a nationwide outbreak (rapid emergence and spread) of a particularly bad bug. The concept of using active surveillance selectively in an outbreak setting is one with which I agree—identifying as many carriers as possible, assessing the “colonization pressure” in your population, all of this can be very helpful, even essential, during outbreaks (as long as one recognizes the limitations of the screening tests).

My point was that active surveillance as an ongoing strategy, in the endemic setting, and for the myriad of resistant organisms now present in our hospitals, is not sustainable. The other point is that active surveillance test results are too often falsely reassuring—we imagine we can identify the reservoir when in reality we cannot. We just don’t know enough yet about patterns of colonization and test performance. Finally, identifying carriers is of little use if healthcare workers aren’t adhering to good infection control practice. I can think of few more worthless practices then chasing down every MRSA carrier in a hospital where fewer than half the healthcare workers wash their hands or properly practice contact precautions.

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