Occurrence and genotypic characterization of C. difficile in food, animals and in the environment in Italy and Switzerland

The aim of this work was to investigate the occurrence of C. difficile ribotypes in sea food, animals and the environment in Southern Italy and in Ticino Canton (Switzerland). A comparison of ribotypes with those associated to human CDI in Ticino Canton was also carried out. Samples of seawater (25), zooplankton (5), sea sediments (5), shellfish (105), river water (5), lake water (8), lake sediments (8) and raw (1) and treated wastewater (1) were collected in different areas of Campania and Basilicata regions, in Southern Italy. In Ticino, rectal swabs from ruminants (150) and piglets (2) and samples of influents (9) and effluents (9) from the 9 largest wastewater purification plants of the region were also collected. Molecular identification, toxin genes detection, toxinotyping and ribotyping were carried out on the isolates. In Italy, C. difficile was isolated from seawater, zooplankton, edible shellfish, river water, lake sediments and in both samples of raw and treated wastewater analyzed. In Ticino Canton C. difficile was recovered from ruminants, piglets and wastewater. Taking all the environmental strains into account, toxinotype V/ribotype 078 was the most common isolate, followed by toxinotype 0/ribotypes 014 and 070, and nontoxigenic strains/ribotype 010. Toxinotype 0 strains were the most frequently isolated in all the meat producing animals investigated, while the most common ribotypes were 001 and 066. Shellfish, a popular food in Southern Italy usually eaten raw or lightly cooked, were found to be contaminated with toxigenic C. difficile; ribotypes 014 and 078 were the most commonly found among these isolates. Some of the ribotypes of C. difficile isolated in Ticino Canton overlapped with those responsible of human CDI in 2010 in the same geographic area. The lack of epidemiological data in Southern Italy on the incidence of CDI prevented us from drawing a similar correlation. The results of the 2008 European survey about the incidence of CDI in European hospitals highlighted that the most prevalent clinical ribotypes recovered in Italy were 078, 001, 014, 106, 126, 018, the same ribotypes we found in shellfish, lake sediments and wastewater in this area. This work points out a possible health risk associated to the widespread diffusion of virulent C. difficile strains, including the hypervirulent C. difficile ribotype 078, in environmental, animal and sea food sources in both Ticino Canton and Southern Italy.