Diversity of MCR-1 producing Enterobacterales isolated in poultry farms in the United Arab Emirates

Background: Although human infections with Mcr-producing Enterobacteriaceae have been reported from the Arabian Peninsula, mcr in strains of animal origin has not been studied. Materials/methods: Ten composite faecal samples were collected in each of four geographically distant poultry farms in Abu Dhabi Emirate. Ten colonies from McConkey agar containing 1mg/L colistin from each sample were PCR-screened for mcr-1,-2,-3,-4,-5. One isolate representing each distinct plasmid profiles were selected for susceptibility testing and for pulsed field gel electrophoresis (PFGE). Transfer of the mcr gene into E. coli K12 was attempted. Plasmids were compared by RFLP using HincII, NdeI and NsiI restriction endonucleases. Results: mcr-1 positive colonies were identified in 36 of the 40 samples. The 40 isolates (37 Escherichia coli, two Klebsiella pneumoniae and one Salmonella enterica) selected were resistant to ampicillin and colistin (MIC range 4->256 mg/L) with variable resistance to 3rd generation cephalosporins, tetracyclines, quinolones, co-trimoxazole and aminoglycosides. Of the 37 E. coli 28 strains were typable by PFGE giving 12 distinct patterns. Plasmids representing 3 molecular masses: >200 kb, 60 kb and 35 kb were successfully transferred from 6, 26 and 4 isolates, respectively. The >200 kb plasmids represented three, the 60 kb plasmids two, and the 35 kb plasmids a single RFLP patterns. Co-transfer of ampicillin, chloramphenicol, tetracycline resistance with the mcr-1 gene was observed in case of the >200 kb plasmid.Conclusions: From the four chicken farms multiple species of Enterobacteriaceae exhibiting a variety of PFGE patterns, carrying the mcr-1 gene on plasmids of 3 distinct molecular weight showing different RFLP patterns were isolated. Similar strains and similar plasmids were present in multiple farms. These data show that the farms are heavily infested with mcr-1 carrying strains with the possibility to transfer it, via the food chain, to humans.