Assessment of the occurrence of MCR producing Enterobacteriaceae in Swiss and imported poultry meat

To determine whether MCR-producing Enterobacteriaceae are present in poultry meat at retail level, 128 fresh meat samples from Switzerland (n=40), Germany (n=69), Hungary (n=6), Denmark (n=6), Austria (n=2), and Italy (n=5), obtained from retail stores were analyzed. The plasmid-mediated colistin resistance gene mcr-1 was detected by PCR in 33 (25.8%) meat samples (5 samples originating from Italy and 28 samples originating from Germany). Thereof, 12 mcr-1 harbouring E. coli were obtained from 12 samples (10 from Germany and two from Italy) by subculturing for further characterization. Despite repeated subculturing, the remaining 21 samples were discarded due to mixed growth with Proteus spp., which possess intrinsic resistance to polymyxins. The isolates belonged to various sequence types (ST) and clonal complexes (CC), including E. coli of the endemic avian and human pathogenic CC10, CC23, and CC155. Further STs included ST156, ST1431 and ST3519, which are associated with humans and animals. Our data highlight the importance of surveillance of retail poultry meat from different countries in context of the global dissemination of MCR-producing E. coli.