Contamination of Australian newborn calf carcasses at slaughter with Clostridium difficile

Abstract In North America and Europe, reports of a genetic overlap between toxigenic strains of Clostridium difficile isolated from humans, livestock and retail meat suggest that food-borne transmission may be occurring. We investigated the prevalence, concentration and genetic diversity of C. difficile on the carcasses ( n  = 300) and in the faeces ( n  = 30) of neonatal veal calves at three abattoirs in Australia in 2013. Selective culture (both direct and enrichment) was performed, and all isolates were characterized by PCR for the toxin genes tcdA , tcdB and cdtA/B and by PCR ribotyping. Prevalence of C. difficile was 25.3% (76/300) on carcasses and 60.0% (18/30) in faeces. Multiple PCR ribotypes (RT) were detected, with four binary toxin-positive RTs accounting for 70.3% (71/101) of isolates; 127 (A + , B + , CDT + , 32.7%), 288 (A – , B – , CDT + , 28.7%), 033 (A – , B – , CDT + , 6.9%) and 126 (A + , B + , CDT + , 2.0%). Viable counts of a subset of samples revealed detectable numbers of C. difficile in 66.7% (10/15) of faecal samples (range 2.0 × 10 3 to 2.3 × 10 6  CFU/mL, median count 2.5 × 10 4  CFU/mL) and in 16.7% (25/150) of carcase samples (range 3 to 33 CFU/cm 2 , median count 7 CFU/cm 2 ). These data further confirm that Australian neonatal veal calf carcasses are contaminated with potentially significant strains of C. difficile at slaughter.