Prevalence of Colistin Resistance inEscherichia coliin Eastern Turkey and Genomic Characterization of anmcr-1Positive Strain from Retail Chicken Meat

Colistin is one of the most effective antibiotics against multidrug resistant Gram-negative bacteria. However, the recent emergence of plasmid-borne mobilized colistin resistance (mcr) genes is considered a serious antimicrobial resistance challenge worldwide. In this study, we report detection of anmcr-1carryingEscherichia coliisolate (named ATAVETmcr-1 Turkey) from retail raw chicken meat in Turkey. Of the 11 (from 500 total tested) phenotypically colistin-resistant isolates, 1 was shown to carry themcr-1gene by PCR. Whole-genome sequencing indicated thatmcr-1was located on a similar to 13 kb-long contig that was almost identical to the corresponding part in pZJ1635, an IncI2 plasmid encodingmcr-1in the same genetic context in anotherE. colistrain. In addition, ATAVETmcr-1 Turkey harboredbla(CTX-M-8),qnrB19,mdf(A),tet(A),sul2,aph(3 '')-Ib,aph(6)-Id, andfloRresistance genes. Phylogenetic analysis based on whole genome and multilocus sequence typing indicated that ATAVETmcr-1 Turkey was more closely related tomcr-1carryingE. coliisolates from food and human clinical samples previously reported from different parts of the world than to those from Turkey. These findings further emphasize the worldwide emergence and spread ofmcrmeditated colistin resistance in bacteria with zoonotic potential within animals and the food chain.

Automated summary

This study detected an E. coli isolate carrying the mcr-1 gene from retail raw chicken meat in Turkey. Whole genome sequencing revealed that this isolate was more closely related to mcr-1 carrying E. coli strains reported from different parts of the world than to those from Turkey. These findings underline the global emergence and spread of mcr-mediated colistin resistance in bacteria with zoonotic potential within animals and the food chain.