Recent reports in Europe and North America of Clostridium difficile being isolated from production animals and retail meats have raised concerns about potential risks to public health. Concomitantly, the incidence of C. difficile infection in humans has increased in the community, with mounting evidence of a genetic overlap between strains isolated from human and animal sources1 .
We investigated the prevalence, concentration and genetic diversity of C. difficile on the carcasses (n=300) and in faeces (n=30) of neonatal veal calves. Sampling took place in April 2013 in three abattoirs supplied by farms in SA and VIC. Selective culture (both direct and enrichment) was performed and isolates were characterised by PCR for toxin genes and PCR ribotyping.
C. difficile prevalence was 25.3% (76/300) on carcasses and 60.0% (18/30) in faeces. Plate counts revealed a concentration of viable C. difficile on carcasses (median 3 cfu/cm2, highest 33 cfu/cm2) and in faeces (mean 2.8 x 105 cfu/mL). The majority of isolates (88.2%) were positive for tcdA/tcdB, 41% of which were also positive for binary toxin genes. Multiple PCR ribotypes (RT) were identified including RT127 comprising 33.3% of isolates. RT127 is genetically related to RT078, the predominant animal ribotype worldwide and increasingly associated with community C. difficile infection in the Northern Hemisphere. RTs QX150 and UK137 were also found in high proportions, 28.4% and 14.7%, respectively. Along with RT127, these RTs have been isolated from humans in Australia in the last decade, albeit in a relatively low number of cases.
These data confirm earlier findings that Australian neonatal calves are a potential source of C. difficile2. Although not quantified, there remains a risk to public health if C. difficile spores on contaminated veal products survive downstream processing and cooking.
We are grateful to Meat & Livestock Australia for their continued support throughout this project.