MRSA and bedbugs?

An ahead-of-print paper in Emerging Infectious Diseases is generating some buzz in the mainstream media. While the findings are interesting, I’m honestly not sure how they got published, being so preliminary.

Like many areas, Vancouver, British Columbia has seen a jump in the prevalence of bedbugs. After finding impoverished patients infested with the bugs, researchers decided to collect some and test them for pathogens–specifically, methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant Enterococcus (VRE). So, they tested 5 bugs from 3 patients. That’s it–it doesn’t even appear to be 5 bugs apiece, but just 5 total. And the bugs were simply homogenized and streaked–not an uncommon way to test bugs for microbes, but one that has pretty severe limitations if you’re really looking at transmission via biting.

They did find MRSA (and VRE)–obviously, or it wouldn’t have made news. VRE was isolated from 1 bug each from 2 patients; MRSA was isolated from 3 bedbugs from the remaining patient. At first read, I thought they’d confirmed the MRSA strains were USA300, but they didn’t even do that–all they did was note the antibiotic susceptibility profiles of the isolates were consistent with USA300 (though headlines are already screaming “flesh eating bacteria isolated from bedbugs!” as you can see from the link up top). However, what we don’t know if whether the bedbugs were simply externally contaminated (perhaps from close contact with their human hosts), or if they were actually carrying the organisms in their salivary glands (as has been previously reported for S. aureus). If it’s the latter, an infection risk seems more plausible, although I suppose a bite from an externally-contaminated bedbug could also introduce organisms into an open wound.

Still, the paper is really, really, really sparse on data. I’ll sum up with words expressed in the newspaper story above:

Medical health officer Dr. Reka Gustafson said the St. Paul’s study is so small that no public health warning is necessary. She noted the superbug MRSA can be found on “doctors’ ties” and chairs in public places and that it’s more important to counsel people “to wash their hands thoroughly and use antibiotics wisely.”

Lowe CF, Romney MG (2011). Bedbugs as Vectors for Drug-Resistant Bacteria Emerging Infectious Diseases