Occurrence And Characteristics Of Escherichia Coli Mcr-1-Like In Rabbits In Shandong, China

Polymyxin is regarded as the last retort to fight against multidrug-resistant (MDR)Enterobacteriaceae. The emergency and spread of polymyxin-associated resistance genemcr-1evoked great panic of no medicine to cure the bacterial infection in society.mcr-1 is widespread in domestic and wild animals. Therefore, continuous monitoring of its prevalence and characteristics is required. In this study, we used a polymerase chain reaction (PCR)-based method to detect themcr-1 of Escherichia coliisolated from rabbits of Tai'an, China, and determined the characteristics of mcr-1-bearing plasmids. A total of 55 non-duplicatedE. coliwas recovered from the swabs of rabbit faeces. Plasmid profiling, plasmid and chromosome PCR, complete genome sequencing, a conjugation experiment, lactose fermentation experiment, multilocus sequence typing and polymyxin resistance tests were performed to determine the characteristics ofmcr-1-bearing plasmids. 14.6% (8/55) of the specimens weremcr-1 positive. Themcr-1-positiveE. coliharboured more drug-resistant genes compared with themcr-1-negative specimens, and results showed four sequence types. Overall, these findings suggested the possible threat of the transmission ofmcr-1from rabbits to humans, especially since the gene is located on transferable plasmids making horizontal transfer relatively easy. Since food-producing animals are necessary for our daily diet, worldwide cooperation is needed in fighting the spread of this drug resistance gene to avoid human infections with MDR pathogenic bacteria.