Escherichia coli of sequence type 3835 carrying blaNDM-1, blaCTX-M-15, blaCMY-42 and blaSHV-12

New Delhi metallo-beta-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 mu g/ml) and meropenem (MIC, 128 mu g/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 beta-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.