Molecular Epidemiology and Colistin Resistant Mechanism of mcr-Positive and mcr-Negative Clinical Isolated Escherichia coli.

Qixia Luo,Yonghong Xiao,Hao Xu,Ping Shen,Chen Huang,Shaoyan Xu,Lanjuan Li,Wei Yu,Kai Zhou,Lihua Guo,Haifeng Lu

doi:10.3389/fmicb.2017.02262

Abstract

Transmissible colistin resistance mediated by the mcr gene has been reported worldwide, but clinical isolates of mcr-negative colistin-resistant Escherichia coli are rarely reported. The aim of this study was to evaluate the mechanism of colistin resistance among mcr-positive and mcr-negative E. coli clinical isolates by performing a molecular epidemiological surveillance. For the first time ever, we show nearly the same isolation ratio for mcr-negative and mcr-positive colistin-resistant clinical isolates (47.5 and 52.5%, respectively), with no demonstrable nosocomial transmission. We provide evidence for the prevalence of the mcr-positive IncX4 plasmid and its high potential for horizontal transfer, with no obvious sequence type (ST) preference. In addition, the minimal inhibitory concentrations (MICs) of colistin of the mcr-negative E. coli isolates were obviously higher than those of mcr-positive isolates. Apart from the usually detected genes, i.e., pmrAB, phoPQ, and mgrB, other genes may be associated with the colistin resistance in mcr-negative E. coli. To the best of our knowledge, this is the first paper to report the molecular epidemiological surveillance and the proper mechanism of colistin resistance in mcr-negative E. coli clinical isolates. Together, the results show that colistin resistance was prevalent not only in the mcr-positive clinical E. coli isolates but also in the mcr-negative isolates.

Highlights

Polymyxin, recently reintroduced in human medicine practice, constitutes one of the last resorts for the treatment of multidrug-resistant Gram-negative bacteria (Nation et al, 2014)
The isolates were obtained from in 16 wards and the patients were from multiple cities in the Zhejiang Province, TABLE 2 | Antibiotic susceptibilities, sequence types (ST), ESBL genes, and mcr-1-harboring plasmid replicon types of E. coli isolates
In China, where colistin is not used in the clinic for the treatment of infectious disease, the extensive use of antibiotics in food animal production, including swine and poultry farming, has increased the risk of transfer of the resistant bacteria to human

Summary

Introduction

Recently reintroduced in human medicine practice, constitutes one of the last resorts for the treatment of multidrug-resistant Gram-negative bacteria (Nation et al, 2014). A plasmid-mediated colistin resistance gene, mcr-1, harbored by Escherichia coli and Klebsiella pneumoniae isolated from animals and hospital inpatients, was first reported in China (Liu et al, 2016). It became popular all over the world (Rapoport et al, 2016; Rolain et al, 2016; Sonnevend et al, 2016), demonstrating a horizontal transfer mechanism for colistin resistance.

Objectives

Methods

Results

Conclusion