Genomic features of colistin resistant Escherichia coli ST69 strain harboring mcr-1 on IncHI2 plasmid from raw milk cheese in Egypt

There is emerging evidence that food of animal origin may be responsible for the spread of multidrug resistant extraintestinal pathogenic Escherichia coli in the community. Here, we describe the emergence of colistin resistance gene, mcr-1, in a strain belonging to the dominant uropathogenic E. coli ST69 lineage. E. coli strain CFSAN061770 was isolated during monitoring of the popular Egyptian raw milk cheese, karish cheese, for the presence of colistin resistance. The complete genome of E. coli strain CFSAN061770 comprises a chromosome of 5,292,297 bp with a G + C content of 50.6%. Further, three plasmids named pEGY1-MCR-1, pEGY2 and pEGY3 of 228,947 bp, 103,234 bp and 87,012 bp were detected, respectively. Plasmid pEGY1-MCR-1 belongs to the IncHI2 incompatibility group and carries the colistin resistance mcr-1 gene flanked by two ISApil elements and forms a composite transposon. It mediates resistance to aminoglycosides (aadA1 and aadA2), phenicol (cmlA1 and floR), sulfonamides (sul3), and tetracycline (tet(A)), and these loci were found clustered in a multidrug resistant region. Plasmid pEGY3 carries a complex multiple resistance locus (CMR) (aph(3')-Ia, strA, strB, sul2, and bla(TEM-1)) encoding resistance to different classes of antibiotics. Interestingly, the closest plasmids to plasmid pEGY1-MCR-1 detected from the NCBI Blast search belonged to the incompatibility group IncHI2 and were from the Kingdom of Saudi Arabia and Qatar which suggests a dissemination of pEGY1-MCR-1-like plasmids in the Middle East. Most striking, and of great public health concern is that strain CFSAN061770 carries five virulence genes (iss, fimH, int& kpsMIII and kpsTIII) which were identified in clinical extraintestinal pathogenic E. coli. Besides that, it carries the astA gene, which codes for the enteroaggregative E. coli heat-stable toxin 1 (EAST1).