Genetics: C. difficile hospital-associated epidemics

Genome sequencing of a large global collection Clostridium difficile isolates from health-care settings is reported this week in Nature Genetics.

C. difficile is the most common cause of infectious antibiotic-associated diarrhea and healthcare-associated infection in developed countries. C. difficile infection and disease prevalence has increased over the past two decades, and this has largely been driven by a hyper-virulent C. difficile clone.

Trevor Lawley and colleagues report the whole-genome sequencing of a geographically and temporally diverse global collection of 151 isolates of the C. difficile epidemic clone, along with 145 additional isolates from the United Kingdom. They are able to trace the emergence and spread of the C. difficile epidemics, and find that the C. difficile epidemic clone 027/BI/NAP1 consists of two distinct lineages, in contrast to previous reports suggesting just one lineage. They show that these two epidemic lineages each emerged in North America in the early 2000s, and that each separately acquired the same fluoroquinolone resistance mutation. They suggest that the common use of fluoroquinolone antibiotics in North America during this time may have provided a selective pressure driving the emergence of these two lineages and the C. difficile epidemic.