Could potatoes play a role in C. difficile transmission?
Clostridioides difficile is a noteworthy cause of diarrhoea in individuals with disturbed gut microbiota, for instance after taking antibiotics for urinary or respiratory infection. It is well known that ingestion of spores is a first step in the infection. Human to human spore transmissions in hospitals or in domestic environment are well recognized. But in recent years there is a huge interest to explore alternative sources and transmission routes of spore transmissions. Food is such an alternative source.
One of the main goals of COMBACTE-CDI is to generate a detailed understanding of the C. difficile epidemiology in Europe, which includes providing up-to-date information on C. difficile in food across Europe. Potato was selected as one of the main staple foods broadly used in all European countries. The strength of this project was in identical protocols for sampling and isolation. Therefore results between different countries are directly comparable. COMBACTE-CDI has collected clinical, animal and food samples in 12 European Countries. The researchers refer to this particular study as the ‘COMBACTE-CDI potato study’ to distinguish this work from other investigations of C. difficile by the same consortium.
In total, 153 samples of potatoes or potato swabs were collected across 12 European countries and 147 were included in the final analysis. From C. difficile-positive potato samples (33/147; 22.5%), they obtained 504 isolates, grouped into 38 PCR ribotypes. Contamination rates between countries varies from 0% to 100% and nine of the 12 countries had contamination rates of less than 10%. The detected PCR ribotypes were diverse and similar to those found in humans, animals and soil. The potato is a food commonly contaminated with C. difficile, although the positivity rates across countries varied substantially. The absence of clonal clusters indicates that there are no clearly successful clonal strains, although the sample size was modest.
Maja Rupnik, Management Board Member COMBACTE-CDI: ‘’Potatoes are typically washed, peeled and cooked before eating, which reduces the risk that they could be a direct source of infection. Nevertheless, potatoes can serve as a vector for introducing C. difficile spores in the household environment and/or food chain, where they could persist. After such indirect exposure, it is possible that ingested C. difficile could multiply, particularly in the presence of disrupted or immature microbiota of a sensitive host (human or pet). In this way, potatoes could have a role in the transmission of C. difficile between community reservoirs.’’
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Our results suggest the high potato contamination rates could have public health relevance. They indicate potatoes can serve as a vector for introducing C. difficile spores in the household environment, where the bacterium can then multiply in sensitive hosts with disrupted or immature microbiota. Potato contamination with PCR ribotypes shared between humans, animals and soil is supportive of this view.Maja Rupnik, Management Board Member COMBACTE-CDI