Escherichia coli of sequence type 3835 carrying bla NDM-1, bla CTX-M-15, bla CMY-42 and bla SHV-12.

New Delhi metallo-β-lactamase (NDM) represents a serious challenge for treatment and public health. A carbapenem-resistant Escherichia coli clinical strain WCHEC13-8 was subjected to antimicrobial susceptibility tests, whole genome sequencing and conjugation experiments. It was resistant to imipenem (MIC, >256 μg/ml) and meropenem (MIC, 128 μg/ml) and belonged to ST3835. bla NDM-1 was the only carbapenemase gene detected. Strain WCHEC13-8 also had a plasmid-borne AmpC gene (bla CMY-42) and two extended-spectrum β-lactamase genes (bla CTX-M-15 and bla SHV-12). bla NDM-1 and bla SHV-12 were carried by a 54-kb IncX3 self-transmissible plasmid, which is identical to plasmid pNDM-HF727 from Enterobacter cloacae. bla CMY-42 was carried by a 64-kb IncI1 plasmid and bla CTX-M-15 was located on a 141-kb plasmid with multiple F replicons (replicon type: F36:A4:B1). bla CMY-42 was in a complicated context and the mobilisation of bla CMY-42 was due to the transposition of ISEcp1 by misidentifying its right-end boundary. Genetic context of bla NDM-1 in strain WCHEC13-8 was closely related to those on IncX3 plasmids in various Enterobacteriaceae species in China. In conclusion, a multidrug-resistant ST3835 E. coli clinical strain carrying bla NDM-1, bla CTX-M-15, bla CMY-42 and bla SHV-12 was identified. IncX3 plasmids may be making a significant contribution to the dissemination of bla NDM among Enterobacteriaceae in China.