CHROMOSOMAL LOCATIONS OF mcr-1 IN Klebsiella pneumoniae AND Enterobacter cloacae FROM DOGS

In November 2015, the emergence of a novel plasmid-mediated colistin resistance mechanism was described. So far, there are only two relevant published reports focused solely on Escherichia coli and Salmonella in Taiwan. This paper describes the emergence of colistin-resistant Klebsiella pneumoniae and Enterobacter cloacae clinical isolates harboring mcr-1 on chromosomes in Taiwan. All four mcr-1-positive isolates were from 63 Klebsiella spp., and the isolated Enterobacter spp. were from diseased dogs and cats at Veterinary Teaching Hospital, National Chiayi University. These four isolates were resistant to colistin, amoxicillin, doxycycline and oxytetracycline, and all mcr-1 genes were located on the chromosome, without any flanking ISApl1 or other insertion sequences. The findings suggest that, in addition to food animals and humans, companion animals can serve as reservoirs of mcr-1, adding another layer of complexity to the rapidly evolving epidemiology of plasmid-mediated colistin resistance in the community. Hence we consider it essential to continue to survey resistance to colistin in these bacteria. Continuous microbiological and molecular surveillance is necessary to assist in early detection and minimize the dissemination of mcr-1.