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Epidemiology and molecular characterization of mcr-1 in Escherichia coli recovered from patients with bloodstream infections in Changsha, central China

Authors Zhong YM, Liu WE, Zheng ZF

Received 24 March 2019

Accepted for publication 27 June 2019

Published 12 July 2019 Volume 2019:12 Pages 2069—2076


Checked for plagiarism Yes

Review by Single-blind

Peer reviewers approved by Dr Cristina Weinberg

Peer reviewer comments 2

Editor who approved publication: Dr Sahil Khanna

Yi-Ming Zhong,1 Wen-En Liu,1 Zhao-Feng Zheng2

1Department of Clinical Laboratory, Xiangya Hospital, Central South University, Changsha, People’s Republic of China; 2Faculty of Laboratory Medicine, Xiangya School of Medicine, Central South University, Changsha, People’s Republic of China

Objectives: The main aim of this study was to investigate the prevalence and molecular characteristics of the mcr-1 gene in Escherichia coli isolates obtained from all patients with bloodstream infections over a year in a Chinese teaching hospital. We also assessed the susceptibility profiles of the mcr-1-positive strains and prognostic impact of this gene on the patients.
Methods: A total of 144 consecutive, non-repetitive E. coli isolates causing bloodstream infections were collected at a teaching hospital in Changsha, China from January to December 2016. The presence of the mcr-1 gene was assessed by PCR. All mcr-1-positive E coli isolates were characterized by antimicrobial susceptibility testing, multilocus sequence typing (MLST), a conjugation experiment, and plasmid replicon typing. Clinical data were obtained from medical records.
Results: The mcr-1 gene was detected in three (2.1%) of the 144 E. coli isolates. The three mcr-1-positive E. coli isolates were resistant to colistin. All three isolates showed a lower resistance to other classes of antibacterials, with all three being susceptible to carbapenems. The MLST results indicated that the three E. coli isolates were assigned to three different sequence types: ST457, ST101, and ST1413, respectively. The conjugation experiment showed that the mcr-1 gene was successfully transferred to the recipient (E. coli EC600) from two isolates, one of which possessed IncI1 replicons and the other of which carried IncHI2 and IncN replicons. The patients with bloodstream infections caused by mcr-1-positive isolates had severe underlying diseases and were cured after antibacterial treatment.
Conclusion: The prevalence of the mcr-1 gene in patients with E. coli bloodstream infection was 2.1% in Changsha, China. The mcr-1-positive E. coli isolates had varied susceptibility profiles, although all three were susceptible to carbapenems. This therapeutic window is crucial given the risk of rapid deterioration in high-incidence areas worldwide.

Keywords: E. coli, mcr-1, colistin resistance, bloodstream infection, clinical characteristics

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