Abstract: During the investigation of the prevalence of multidrug-resistant bacteria from food-producing animals, an mcr-1-carring multidrug-resistant strain of Proteus mirabilis was isolated and designated as F160211. Its drug-resistant profile and genotype were further investigated. The isolate was identified by 16S rRNA gene amplification and its drug-resistant profile was defined using a disk-based test and minimum inhibitory concentration (MIC) test. The drug-resistance genes were amplified by polymerase chain reaction (PCR). At last, the replication type of mcr-1-carring plasmid was analyzed. The results showed that the isolate F160211 was identified as P. mirabilis, and it was resistant to penicillin, first- and second-generation cephalosporins, macrolides, aminoglycosides, amphenicols, tetracyclines, sulfanilamides and rifamycins, and was intermediate to furans, polypeptide and quinolones, and was susceptible to third- and fourth-generation cephalosporins, monobactams, carbapenems, glycylcyclines and polymyxins. The drug-resistance genes that F160211 carried included blaCTX-M-1, blaCTX-M-9, blaTEM, blaOXA-1, mph(A), qnrS and mcr-1. The replicon PCR showed that mcr-1 was located in a IncI2 type plasmid, which was similar to pHNSHP45. These results showed that the mcr-1-harboring host bacteria have been extended from Escherichia coli and Salmonella to P. mirabilis and that the grim problem of multidrug-resistant bacteria from food-producing animals will pose a great threat to food safety and public health.

Key words: mcr-1, food-producing animals, multidrug resistance, minimum inhibitory concentration (MIC), Proteus mirabilis