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Infect Drug Resist. 2018 Dec 28;12:105-110. doi: 10.2147/IDR.S190269. eCollection 2019.

Prevalence and molecular characteristics of mcr-1 gene in Salmonella typhimurium in a tertiary hospital of Zhejiang Province.

Lu J1, Quan J2,3, Zhao D2, Wang Y2,3, Yu Y2,3, Zhu J1.

Author information

1
Department of Laboratory, Quzhou People's Hospital, Quzhou, Zhejiang, China, qzhosp@163.com.
2
Department of Infectious Diseases, College of Medicine, Sir Run Run Shaw Hospital, Zhejiang University, Hangzhou, Zhejiang, China.
3
Key Laboratory of Microbial Technology and Bioinformatics of Zhejiang Province, Hangzhou, Zhejiang, China.

Abstract

Objectives:

mcr-1 gene has been widely reported in the world. This study aimed to analyze the prevalence and molecular characteristics of mcr-1 gene in Salmonella typhimurium from Quzhou People's Hospital.

Materials and methods:

A total of 62 S. typhimurium isolates were isolated and preserved in our laboratory from 2007 to 2016. PCR was used to screen plasmid-mediated colistin resistance gene, mcr-1. For mcr-1-positive isolates, susceptibilities to colistin and other antibiotics were assessed using broth microdilution or agar dilution methods. The genetic location of mcr-1 was determined by analysis of pulsed-field gel electrophoresis profiles of S1-digested genomic DNA and subsequent Southern blot hybridization. The multi-locus sequence type and other drug resistance genes found in the mcr-1-positive isolates were analyzed by performing whole genome sequencing. Genetic environment of mcr-1 gene was analyzed by RAST and Easyfig.

Results:

A total of three S. typhimurium isolates were identified to be mcr-1 positive, with the prevalence rate of 4.8% (3/62). The minimum inhibitory concentration values of colistin for all these isolates were 8 µg/mL. The three mcr-1-positive isolates carried mcr-1 gene on two different types of plasmids having the sizes of ~54.7-78.2 kb and 310.1 kb, respectively. All the three isolates belonged to ST34 and carried various resistant genes.

Conclusion:

Colistin-resistant, mcr-1-positive S. typhimurium isolates belonging to ST34 have been isolated from Quzhou People's Hospital. Surveillance needs to be strengthened to identify colistin resistance and prevent the spread of drug-resistant bacteria in the hospital.

KEYWORDS:

Salmonella typhimurium; colistin; mcr-1

Conflict of interest statement

Disclosure None of the authors have any personal or financial involvement with the organizations that have financial interest in the content of this study. The authors report no conflicts of interest in this work.

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