Methods currently applied to study the prevalence of Clostridioides difficile in foods

Clostridioides difficile is responsible for most cases of antibiotic- and hospital-associated diarrhoea. Several studies have demonstrated the presence of C. difficile in different foods such as meat, raw milk, vegetables and seafood, which supports the hypothesis that foods contaminated with spores may be contributing to the exposure to and transmission of C. difficile. Generally, the prevalence of C. difficile in foods is low and there is no standard methodology for its isolation. Available methods have been optimized for stool samples rather than foods. In the majority of the studies, a similar base culture medium has been used and different selective and enrichment compounds are further added, which is, sometimes, controversial. Despite the extensive use of cycloserine and cefoxitin, as well as moxalactam and norfloxacin, many authors believe that the use of these selective supplements had an adverse effect on the recovery of C. difficile and only enabled recovery of resistant isolates from food samples. Another example is the use of sodium taurocholate to potentiate the germination of C. difficile spores; there are studies reporting that the addition of this component in the enrichment medium did not exert a beneficial effect on C. difficile recovery. Variations in sample amounts, dilution factors, incubation times, among others, may also affect the recovery of C. difficile from foods. Numerous studies have recently emerged, since there is increasing interest in C. difficile as a potentially foodborne pathogen. Thus, the purpose of this review is to summarize the methodologies currently used on the isolation/detection of C. difficile in foods and its subsequent characterization and typing.