Complete genome sequence of mcr-1-harboring Escherichia coli discovered from Mink

BACKGROUND: The emergency of polymyxin resistance gene mcr-1 located on plasmids has aroused great concern about the lack of medicine for bacterial infection. METHODS: In this study, a strain of Escherichia coli harboring mcr-1 was recovered from mink liver. The drug-resistant genes were determined by PCR. Identification of bacteria was determined by combination of biology phenotype, chemical tests, 16SrRNA, minimum inhibition concentration and mass spectrometry. Complete genome sequence was done with the method of Nanopore. The plasmid map was drawn with Snapgene Viewer software. RESULTS: Results of PCR and complete genome sequencing of nrcr-1 were all positive. Results showed the bacteria were Gram negative. lactose test positive, indole test positive, MR test positive and VP test Negative. The results of mass spectrometry showed that DH5 alpha was the reference strain, and the MLST Test showed the strain of Escherichia coli was ST140.The complete genome sequence showed that the whole length was 5,316,854bp and contained three contigs, one of which was chromosome and the other two plasmids. CONCLUSIONS: Drug resistant gene gryA was located on chromosome while mcr-1 and sul antibiotic genes were located on plasmid 1 and Bla(CTX-M-1) was located on plasmid 2. To our knowledge, this is the first report of a polymyxin resistance plasmid harboring Sul2.