Biogeographic distribution and molecular epidemiology of Clostridioides (Clostridium) difficile in Western Australian soils

Clostridioides (Clostridium) difficile is a leading cause of infectious diarrhea in humans and production animals and can be found in a variety of environmental sources. The prevalence and diversity of multi-locus sequence type clade 5 strains of C. difficile in Australian production animals suggest Australia might be the ancestral home of this lineage of One Health importance. To better understand the role of the environment in the colonization of humans and animals in Australia, it is important to investigate these endemic sources. This study describes the prevalence, molecular epidemiology, and biogeographic distribution of C. difficile in soils of Western Australia. A total of 321 soil samples from remote geographical locations across the eight health regions of Western Australia were screened for C. difficile and isolates characterized by PCR ribotyping and toxin gene profiling. C. difficile was isolated from 31.15% of samples, with the highest prevalence in the Perth Metropolitan Health Region (49.25%, n = 33/67). Overall, 52 different strains [PCR ribotypes (RTs)] were identified, with 14 being novel, and 38% (38/100) of isolates being toxigenic, the most common of which was RT014/020. Five unique novel isolates showed characteristics similar to C. difficile clade 5. This is the first study of C. difficile isolated from soils in Australia. The high prevalence and heterogeneity of C. difficile strains recovered suggest that soils play a role in the survival and environmental dissemination of this organism, and potentially its transmission among native wildlife and production animals, and in community and hospital settings.