CRE – too weak to spread!?

superbug

(Photo: thinkprogress.org)

In the May issue of ICHE, Weber et al. published their findings of a study looking at the environmental contamination of rooms occupied  by patients colonized or infected with CRE. In addition to their observations they actively inoculated test surfaces with 102 CRE (which I find rather low). They found that the contamination in the patients’ room was infrequent (8.4%) and at low levels (5.1 CFU/120cm2). With the single exception of K. pneumoniae on formica, alle CRE had a less than 15% survival at 24 hours and a 0% survival after 72 hours.

Should we just conclude that the chance of CRE transmission from the environment is very low?

I believe that this conclusion would be too early and probably wrong. The survival of micro-organisms in the environment is clearly strain dependent and while the authors used clinical isolates they did not mention if they included a strain that has proven its ability to spread (eg. outbreak isolates). In general multi-resistant bacteria may loose some of their fitness – including the ability to survive in the environment – but survival studies like those of Kramer et al. show survival of multiple weeks for E. coli and Klebsiella spp.

Furthermore, Weber et al. do not state at which point in regard to cleaning the rooms were examined, for how long the rooms were occupied, or which patient’s site were colonized or infected. All of the above would most certainly influence the measured outcome.

Last but not least, does anyone (e.g. you – the readers) know the “incubation time” for colonization? How long does it take for a patient to pick-up CRE from his or her environment? During past outbreak work-ups (obviously none-CRE – I work in the Netherlands), I have seen patients picking-up the outbreak strain within hours after admission, even before having had the chance to meet their HCWs (including their contaminated hands).

Thus before hoping that CRE is to weak to spread and assuming that the environment’s auto-sterile abilities kick in fast enough – wait for future studies. Until than, if someone tries to place me in any of those CRE-pre-occupied rooms, give it a good scrub.

  1. Weber et al. Carbapenem-resistant enterobacteriaceae: Frequency of Hospital Room Contamination and survival on vatious inoculated surfaces. Infect Control Hosp Epidemiol 2015;36:590-93
  2. Kramer et al. How long do nosocomial pathogens persist on inanimate surfaces? A systematic review. BMC Infectious Diseases 2006, 6:130
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4 thoughts on “CRE – too weak to spread!?

  1. Hi Andreas I agree with you. I think we’d be foolish to discount the role of the environment in CRE transmission. They are enteric bacteria afterall, adapated to survive in the gut, so they will survive on surfaces too. Our study demonstrated a much longer survival time (measured in months) from a higher inoculum – and I’ve also noted considerable strain variation https://reflectionsipc.com/2014/03/18/cre-can-survive-on-dry-surfaces-for-longer-than-you-may-expect/

    Also, I think an 8% contamination rate of surfaces is fairly high – certainly high enough to be important in terms of onward transmission!

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  2. I also agree Andreas. I have several questions. What surfaces were inoculated? ie. . bed rail, privacy curtain, chair, bed linen. . Second question what surface materials were they made of? ie. . stainless steel, cotton, polyester, laminate. . Different surface materials can provide supportive environments for microbes.

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  3. I too agree. Unlike MRSA (and staphylococci in general) or C. diff (endospores), CRE is an enteric and may just naturally not do well in the environment. G negs have thinner cell envelopes (including PEG thickness) that make them naturally vulnerable to dessication, uv, etc….BUT, that does not mean it can’t quickly be colonizing living surfaces, if not environmental surfaces.

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