Wild mice in and around the city of Utrecht, the Netherlands, are carriers of Clostridium difficile but not ESBL-producing Enterobacteriaceae, Salmonella spp. or MRSA

Mice in buildings are a hygiene hazard because they harbour several zoonoses and animal diseases. The aim of this study was to gather information on specific bacteria in house mice caught in the urban environment. Mice caught in snap traps during pest control activities were collected in and around the city of Utrecht, the Netherlands, during May-June 2014, October-November 2015 and September-November 2016. The gut contents were analysed for ESBL/AmpC-producing Enterobacteriaceae, Salmonella spp., and Clostridium difficile and the buccal cavities were swabbed for methicillin-resistant S. aureus (MRSA). In total, 109 house mice (Mus musculus) and 22 wood mice (Apodemus sylvaticus) were examined. One mouse was found positive for Enterobacter spp. Salmonella spp. and MRSA were not found. Of n=80 mice, 35.0% carried C. difficile (ribotypes in descending order of frequency: 014/020, 258, 002, 005, 013, 056, 081 and two unknown ribotypes). In conclusion, mouse droppings are a hazard for transmission of C. difficile to humans and their environment.