Laboratory-based surveillance of Clostridium difficile infection in Australian healthcare and community settings, 2013-2018.

Objectives In the early 2000s, a binary toxin (CDT)-producing strain of Clostridium difficile, ribotype (RT) 027, caused extensive outbreaks of diarrhoeal disease in North America and Europe. This strain has not established in Australia and there is a markedly different repertoire of circulating strains compared to other regions of the world. The C. difficile Antimicrobial Resistance Surveillance (CDARS) study is a nationwide longitudinal surveillance study of C. difficile infection (CDI) in Australia. Here, we describe the molecular epidemiology of CDI in Australian healthcare and community settings over the first 5 years of the study, 2013–2018. Methods Between 2013 and 2018, 10 diagnostic microbiology laboratories from five States in Australia participated in the CDARS study. From each of five states, one private (representing community) and one public (representing hospitals), submitted isolates of C. difficile or PCR-positive stool samples during two collection periods per year, February-March (summer/autumn) and August-September (winter/spring). C. difficile was characterised by toxin gene profiling and ribotyping. Results A total of 1523 isolates of C. difficile was studied. PCR ribotyping yielded 203 different RTs, the most prevalent being RT014/020 (n=449, 29.5%). The epidemic CDT+ RTs 027 (n=2) and 078 (n=6), and the recently described RTs 251 (n=10) and 244 (n=6) were not common, while RT126 (n=17) was the most prevalent CDT+ strain. Conclusions A heterogeneous C. difficile population was identified. C. difficile RT014/020 was the most prevalent strain found in humans with CDI. Continued surveillance of CDI in Australia remains critical for the detection of emerging strain lineages.