Clostridium difficile is the leading cause of healthcare-associated infection. As incidence rises, its epidemiology is also evolving. 20-50% of cases are now community-acquired; C. difficile cases arise from more diverse sources than previously thought. In this study, we investigated the diversity of C. difficile within a community hospital.
Stool samples were collected from symptomatic adults with a positive C. difficile PCR admitted to Duke Regional Hospital from 7/2016 to 7/2017. Healthcare-associated CDI was defined by any admission to a hospital, nursing or dialysis facility in the preceding 30 days. C. difficile was isolated by ethanol shock followed by plating on CDSA media. DNA was extracted using a chelex-based protocol. PCR ribotyping was conducted using the Bidet primers and agarose gel electrophoresis. A dendrogram was constructed in Bionumerics by the un-weighted pair-group method with the threshold for identical strains set at 95% similarity.
C. difficile was successfully isolated from 85% of submitted specimens. For this pilot study, PCR ribotyping was performed on a convenience sample of 70 isolates. C. difficile exhibited substantial diversity: 47 distinct ribotypes were observed among 70 isolates (figure 1). 14 clusters involving identical strain types were observed, totaling 35 isolates. Identical strain types suggestive of direct transmission were evenly split between hospital- (18 of 35, 51%) and community-acquired (17 of 35, 49%) cases. The median time between clustered cases was 50 days (range: 7 to 331 days). 35 of 70 (50%) of all isolates exhibited entirely unique strain types.
C. difficile isolates in our community hospital exhibited tremendous genetic diversity. The high proportion of strains with entirely unique ribotypes suggests diverse sources of acquisition. These results are consistent with a growing body of literature in which 30-50% of C. difficile isolates are genetically distinct, even when direct transmission was suspected. We are currently expanding our survey to include a network of regional hospitals and clinics, with the goal of better characterizing C. difficiles diverse and still poorly understood sources.
Figure 1: Dendrogram of C. difficile PCR ribotypes.
V. G. Fowler Jr., None
D. J. Anderson, None