Characterization of colistin resistant Enterobacteriaceae and Acinetobacter strains carrying mcr genes from Asian aquaculture products
In this study, we characterised seventeen bacterial strains (Escherichia coli, Klebsiella pneumoniae, Acinetobacter baumannii and A. nosocomialis) resistant to colistin originating from retailed aquaculture products imported from Vietnam to the Czech Republic. The mcr-1.1 gene was found located on plasmid types IncHI2, IncI2, IncX4 as well as on rarely described plasmid types IncFIB-FIC and IncFIB(K), phage-like plasmid p0111, or in the chromosome of E. coli. One E. coli strain carried the mcr-3.5 gene on IncFII(pCoo) plasmid in addition to mcr-1.1 gene located on IncHI2 plasmid. K. pneumoniae was found to carry the mcr-1.1 and mcr 8.2 genes on IncFIA(HI1) plasmid. The mcr-4.3 gene was found on similar untypeable plasmids of A. baumannii and A. nosocomialis strains pointing to possible interspecies transfer of plasmids carrying the mcr-4 gene. Our results highlight that aquaculture products of Asian origin can represent an important source of variable plasmids carrying mcr genes. The results showed an involvement of phages in the incorporation of the mcr-1 gene into plasmids or chromosome in E. coli strains from aquaculture. The detection of E. coli with the mcr-1 gene on chromosome point out risks associated with the stabilization of the mcr genes on a bacterial chromosome.