Plasmid-mediated colistin resistance in Escherichia coli from the Arabian Peninsula

Objectives Searching for the presence of the mcr-1 gene in colistin resistant Enterobacteriaceae in countries of the Arabian Peninsula. Methods Seventy-five independent, colistin resistant Enterobacteriaceae strains isolated from clinical cases in Bahrain, Kuwait, Oman, Saudi Arabia and the United Arab Emirates were tested by PCR for the mcr-1 gene. mcr-1 positive strains were genotyped, and their antibiotic susceptibility was established. The mcr-1 containing plasmids were mobilized into Escherichia coli K-12 and their sequence was determined. Results Four E. coli isolates (two from Bahrain, one from Saudi Arabia and one from the United Arab Emirates) were identified carrying the mcr-1 gene on conjugative plasmids. They belonged to global multidrug resistant E. coli clones, i.e. ST648, ST224, ST68 and ST131, respectively. One strain carried the bla_NDM-1 carbapenemase gene. Three strains carried mcr-1 on IncI2 type plasmids, one of them also harboring a bla_CTX-M-64 gene. In the fourth strain mcr-1 was located on a 240 kb IncHI2 plasmid co-harboring 13 other resistance genes. Conclusions This is the first report on the presence of the plasmid-coded mcr-1 gene in a variety of multi-resistant clinical isolates from the Arabian Peninsula indicating that several commonly used antibiotics can potentially facilitate the spread of mcr-1 carrying strains, or directly, mcr-1 containing plasmids.