Acinetobacter contamination: is anywhere safe?

A study from New York City describes an environmental survey of contamination with antibiotic-resistant Gram-negative bacteria on surfaces in the community. The authors hypothesise that resistant Gram-negatives could be carried by staff, patients and visitors beyond the confines of the hospital.

Almost 500 environemntal samples were collected from surfaces in the public areas of six hospitals and surrounding communities (<1 mile from the hospital) (443 samples), with a further surfaces from communities >1.5 miles from any hospital as a control (50 samples). A total of 70 GNR were identified (Figure), mostly fairly inoccousous species from a human disease viewpoint. However, some potential human pathogens were identified (Table).

Figure: breakdown of Gram-negative rods identified from surfaces in public areas of the hospital and surrounding community.GNR contam

Table: potential human pathogens identified from surfaces in public areas of the hospital and surrounding community.

n % Species
15 3.0 Acinetobacter baumannii
3 0.6 Citrobacter freundii
2 0.4 Escherichia coli
2 0.4 Stenotrophomonas maltophilia
1 0.2 Enterobacter cloacae

Some other important findings:

  • All of the A. baumannii isolates were resistant to ceftazidime, and one was resistant to imipenem (i.e. carbapenem-resistant). Eleven of the 15 were clonally related to one another and to a patient isolate from one of the hospitals.
  • One of the S. maltophilia isolates carried an integron-encoded VIM carbapenemase, which is potentially transmissible to other Gram-negative species (including Enterobacteriaceae).  
  • Each sample was cultured in an enrichment broth, and the broth was probed for the presence of a range of beta-lactamase genes (including ESBLs and carbapenemases). No beta-lactamases were detected (other than the S. maltophilia isolate). I suspect the picture would have been rather difference in New Dehli!
  • Although the survey included both surfaces in public areas of hospitals and in the community, it seems that most of the A. baumannii were identified on surfaces in the community.

So, is it a surprise to see environmental contamination with antibiotic-resistant Gram-negatvies on touch-surfaces in the community? Not really, A. baumannii in particular can survive on surfaces for ages, and ‘mimics’ Gram-positive bacteria in terms of its environmental longevity (i.e. months / years). That said, I performed a similar study looking for MRSA on touch surfaces in the community in London, and didn’t find any. More importantly, do we need to do anything about this? As the authors state, A. baumannii can be virtually impossible to eliminate from hospital surfaces without resorting to hydrogen peroxide vapour. So is it time to roll hydrogen peroxide vapour into your local Pizza Hut? Clearly not. You’d hope that cleaning and disinfection protocols, which should deal with this sort of contamination, are already established in these public places, but it would be prudent to reinforce these basic hygienic practices. Also, I agree with the authors that these findings represent and opportunity for the promotion of hand hygiene in the community.

The authors use strong words to describe NYC as ‘plagued’ with resistant Gram-negative bacteria, and a ‘dismal failure to control A. baumannii.’ If this epidemic continues, we can expect to see the focus of the problem – and the target for our interventions – shift from the acute hospital setting to encompass the community.

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4 thoughts on “Acinetobacter contamination: is anywhere safe?

  1. Why is my first response to this sort of paper
    1. Lab contamination
    2. Lab misidentification
    3. Lab misreporting of breakpoints
    Maybe it’s because I’ve reviewed to many papers written by people who seem to have only a vague grasp of laboratory methods. Trouble with automated lab machines is they have a habit of spewing out complete rubbish which is great material for publication in unsuspecting journals. I’m sure not the case here but the devil in these papers is really in the detail.

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    • Why? Because it’s plausible, and has happened before. There were some spurious reports of MRSA contamination in public places in the 2000s, which were subsequently shown to be complete rubbish (dodgy contract test lab reporting methicillin-resistant coag-neg staph as MRSA): http://www.ncbi.nlm.nih.gov/pubmed/16242211

      In this case, I’d be surprised if the results are not legit. It’s a reputable clinical test lab, with each colony speciated by API and tested for antimicrobial susceptibility using agar dilution (not automated system).

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  2. Hi Jon
    No reason to doubt these results, but it is worthwhile mentioning that bacteria such as Acinetobacter and Stenotrophomonas survive as comfortably in the environment as they do in humans, so not too surprising to find such isolates. I don’t think we can insulate ourselves from such exposure and as you mention, the antibiograms of such isolates are probably of more importance.
    Michael

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    • Thanks Michael – agree with you that we have not reason to question these data. The non-fermenters (particularly Acinetobacter and Steano) will survive on dry surfaces for an exceptional length of time. And in a sense masquerade as Gram-positive in this respect. That said, the Enterobacteriaceae are also able to survive on dry surfaces for a surprising length to time – particularly some strains of Klebsiella. I published a paper on this with Yale earlier in the year, finding that CRE could survive for weeks on dry surfaces. You can see the wide variation in surface survival in three strains of K. pneumoniae that I tested here (range 6 weeks).

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