Emergence of a Multidrug-Resistant ST 27 Escherichia Coli Co-Harboring Blandm-1, Mcr-1, and Fosa3 from a Patient in China

In this study, we report a clinical isolate of a carbapenem-, colistin-, and fosfomycin-resistant Escherichia coli isolate DC-3737 co-harboring bla NDM-1 , mcr-1 , and fosA3 from an inpatient in China. Antimicrobial susceptibility testing, polymerase chain reaction, multi-locus sequence typing, conjugation experiment, and Southern blot hybridization were performed on E. coli DC-3737 isolated from the wound. Plasmid analysis is presented and the locations of bla NDM-1 , mcr-1 , fosA3 , and other resistance genes were identified as well. E. coli DC-3737 was resistant to ampicillin, ceftriaxone, ceftazidime, ciprofloxacin, levofloxacin, gentamicin, tobramycin, trimethoprim–sulfamethoxazole, imipenem, meropenem, ertapenem, fosfomycin and colistin, and with intermediate susceptibility to amikacin. It was typed as sequence type 27. The isolate possessed bla NDM-1 , mcr-1 , fosA3 , bla CTX-M-9 , bla TEM-1 , aac (6 ′ )-Ib-cr and sul1 simultaneously. In addition, the mutations in quinolone resistance-determinant regions (QRDRs) such as Ser83Leu and Asp87Asn in gyrA , and Ser80Ile in parC were detected. Conjugation assays revealed that bla NDM-1 , fosA3 , sul1 , mcr-1 , and bla CTX-M-9 genes could successfully transfer their resistance phenotype to E. coli strain J53. Plasmid analysis and Southern hybridization showed that DC-3737 possessed Z-type self-transmissible plasmid bearing bla NDM-1 , fosA3 , and sul1 . Moreover, mcr-1 , bla CTX-M-9 , and bla TEM-1 were located on a ~60-kb IncFIB type self-transmissible plasmid. This is the first report of bla NDM-1 , mcr-1 and fosA3 co-harboring in E. coli in China. Moreover, it is also the first description of the co-harboring of bla NDM and fosA3 in a single Z plasmid in Enterobacteriaceae species. The identification of E. coli DC-3737 co-harboring bla NDM-1 , mcr-1 , and fosA3 in this study highlights the need to increase epidemiologic surveillance and the need for new classes of antibiotics to address multidrug-resistant bacteria.