Clostridioides difficile infection (CDI) is a notable cause of infectious diarrhoea worldwide. In Europe, the estimated number of CDI cases in 2011–12 was 123,997 (95% confidence interval (CI): 61,018–284,857), based on a survey of healthcare-associated infections performed by the European Centre for Disease Prevention and Control (ECDC) [1]. In 2016, as part of C. difficile surveillance performed by ECDC, 556 hospitals from 20 countries covering 24 million patient-days reported 7,711 CDI cases [2]. The symptoms can range from mild diarrhoea to potentially fatal pseudomembranous colitis. While historically regarded as a typical healthcare infection, community CDI is increasingly recognised [3].
In CDI, human-to-human transmission plays a major role, but other infection sources and transmission routes are under investigation. C. difficile has been repeatedly isolated from various foods worldwide, and it is feasible that some foods could be important vectors for its widespread dissemination [3]. Some important healthcare-associated C. difficile PCR ribotypes (RT) such as RT 027 and RT 001/072 tend to spread clonally within a single hospital, region or country, while others such as RT 014, RT 002 and RT 015 do not exhibit country-based clustering and are most likely disseminated across Europe by other sources possibly including the food chain [4]. Confirmed cases of food-associated CDI have so far not been described [3].
Existing evidence suggests that potatoes, which represent a major staple food consumed worldwide, could contribute to the spread of C. difficile. Potatoes have the highest C. difficile contamination rates among all vegetables tested to date; the proportion of C. difficile-positive retail potato samples ranges from 25.7% (18/70) to 53.3% (24/45) [5,6]. By contrast, the highest positivity rate in other types of vegetables such as leaf vegetables, ginger, sprouts and ready-to-eat salads is 9.4% [5–8] and in meats and meat products, reported positivity rates are typically below 20% [8,9]. Additionally, diverse and clinically relevant C. difficile PCR ribotypes have been previously recovered from potatoes. Certain PCR ribotypes such as RT 014/020, which are suggested to spread by non-clonal transmission networks [4], are among those often detected on potatoes [5,6]. Furthermore, potatoes are frequently imported and exported between countries. A previous study from Slovenia reported that 78.9% (15/19) of C. difficile-positive retail potatoes were imported from more than 10 countries on three different continents [6].
Here we present the results of a European-wide study on C. difficile contamination of retail potatoes. Identical protocols for sampling and isolation were used for all 12 studied countries, enabling a direct comparison of the positivity rates of C. difficile on potatoes.
FoodWorld 