Monday, September 30, 2013

Everything old is new again, with WGS!

As we’ve pointed out, whole genome sequencing (WGS) is the hottest new tool to help us decipher the epidemiology of healthcare-associated pathogens. Last week’s NEJM included a study using WGS to investigate the molecular epidemiology of C. difficile disease (CDD) in Oxfordshire, UK. In a 3.6 year study that included 1223 CDD patient isolates, the investigators found that only 333 were genetically related to at least one previously obtained isolate. Of those 333, only 126 (38%) had nosocomial exposure to the earlier patient. And the finding receiving the most attention: 45% of strains isolated were genetically distinct from all previous isolates.

The take home point? In current hospital settings (where we isolate every known CDD patient and use enhanced environmental measures to try to eradicate their C. difficile spores), symptomatic CDD cases are no longer the major reservoir for C. difficile acquisition. Focusing only on transmission prevention, then, will have a limited impact (antimicrobial stewardship, anyone?). Most obviously, further work is clearly needed to identify other sources of exposure and acquisition of C. difficile.

This may come as news to many, but probably not to Matt Samore, who made a similar observation….in 1994.

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