Clostridium difficile PCR Ribotype 014 lineage in Australian humans and pigs

PCR ribotype (RT) 014 is an extremely successful lineage of C. difficile, being consistently among the most common RTs found in human CDI in Europe and currently the most prevalent RT in Australia, accounting for ~25% of CDI cases. In 2013, we conducted a prevalence study of C. difficile in 21 piggeries across 5 states in Australia and quite unexpectedly found RT014 to be the most prominent RT in neonatal pigs, accounting for 23% (n=26/154) of isolates. On the basis of RT data alone, one could suggest that zoonotic (animal to human) or anthroponotic (human to animal) transmission of RT014 is occurring. The aims of this study were two-fold. Firstly, to further define the extent of genetic overlap and to detect evidence of potential transmission events, high resolution WGS and core genome phylogenetics were performed on a collection of RT014 isolates of human and porcine origin. Secondly, the overall genetic repertoire of this RT014 strain collection was investigated by pan genome analysis and characterisation of the C. difficile RT014 resistome, mobilome and virulence potential.