Low prevalence of mobilized resistance genes bla NDM , mcr-1 , and tet (X4) in Escherichia coli from a hospital in China.

The emergence and spread of carbapenemase genes, colistin resistance genes , and tigecycline resistance gene (X) represent a significant threat to clinical therapy and public health. In this study, we investigated the presence of carbapenemase genes, , and (X) in 298 strains obtained from a teaching hospital in China. In total, eight (2.68%), six (2.01%), and one (0.34%) isolates carried , , and (X4), respectively. The gene was located on IncX3 ( = 4), F2:A-:B- ( = 3), and F2:A1:B1 ( = 1) plasmids, with high similarity to multiple plasmids belonging to the same incompatibility type from Enterobacteriaceae. Six MCR-producing strains contained -carrying IncI2 plasmids, organized similarly to other -bearing IncI2 plasmids from animals in China. The gene located within a typical transposition unit (IS--Δ) was inserted near to generate 5-bp direct repeats in four -positive plasmids. The (X) and another four resistance genes [(A), , and Δ(F)] were co-located on an IncX1 plasmid, highly similar to other (X4)-carrying IncX1 plasmids from and of animal or food origin, except that the conjugative transfer region of IncX1 plasmids was absent in our plasmid. Although a low prevalence of , , and (X) was observed in from patients in this study, their dissemination associated with some successful pandemic plasmids is of great concern. The continued surveillance of these crucial resistance genes in patients should be strengthened.