Clostridium difficile — But from Where?

Clostridium difficile is a leading cause of both healthcare-associated diarrhea and hospital-acquired infection. With today's more-virulent strains, such illness causes considerable morbidity and mortality. Although C. difficile infection (CDI) is almost universally preceded by antibiotic therapy, which may have ended weeks or months before symptom onset (JW Infect Dis Feb 29 2012), the source and transmission route of such infection often cannot be identified.

Now, investigators have published the results of an extensive investigation of C. difficile transmission dynamics in Oxfordshire, U.K. From September 2007 through March 2010, 29,299 unformed stool samples from 14,858 individuals (inpatients and outpatients) were tested by enzyme immunoassay for C. difficile toxins; samples that tested positive were cultured. A total of 1276 C. difficile isolates were subjected to multilocus sequence typing, which revealed 69 distinct strains.

Analysis of hospital admissions and ward-movement data for each patient with CDI, assuming an 8-week maximum infection period and a 12-week maximum incubation period, showed that 66% of cases were not linked to known cases, and only 23% had a credible ward-based source. When the analysis was adjusted for chance meetings of patients within the hospital, only 16% of cases were linked by probable transmission events.