Clostridium difficile in vegetables, Canada

BACKGROUND: Clostridium difficile is an important gastrointestinal pathogen of humans and animals. It has been isolated from various foods, including meat and ready-to-eat salads, and concern has been expressed regarding food as a possible source of human C. difficile infection (CDI). AIMS: We sought to isolate C. difficile from a variety of vegetables obtained from local grocery stores and to characterize these isolates. MATERIALS AND METHODS: Vegetables were purchased from 11 different grocery stores in Guelph, Ontario, Canada between May and August 2009. Enrichment culture was performed and isolates were characterized by ribotyping, PFGE, toxinotyping and PCR detection of toxin genes. RESULTS: Clostridium difficile was isolated from 4.5% (5/111) of retail vegetables. Two different ribotypes and two different toxinotypes were identified. Three isolates were ribotype 078/NAP 7/toxinotype V, possessing all three toxin genes. The other two isolates shared a ribotype with a toxigenic strain previously found in humans with CDI in this region. DISCUSSION: Contamination of vegetables was found at relatively low levels, however, all isolates were toxigenic and belonging to ribotypes previously associated with CDI. CONCLUSIONS: Contamination of vegetables with CDI-associated isolates can occur and although the implications for food safety practices remain elusive, the presence of toxigenic isolates suggests vegetables could be a source of C. difficile in humans.