Colistin-Resistant mcr-Positive Enterobacteriaceae in Fresh Vegetables, an Increasing Infectious Threat in China

•Large-scale study showed high prevalence of mcr-1 in fresh vegetables in China.•Multiple mcr-1-positive E. coli isolates with different MLSTs were found in the same vegetable sample.•Dissemination of mcr-1 mediated by highly similar IncX4 or IncI2 plasmids.•IncHI2/ST3 plasmid carrying 14 resistance...

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Bibliographic Details
Published in:International journal of antimicrobial agents 2019-07, Vol.54 (1), p.89-94
Main Authors: Liu, Bao-Tao, Li, Xuyong, Zhang, Qidi, Shan, Hu, Zou, Ming, Song, Feng-Jing
Format: Article
Language:English
Subjects:
Colistin resistance
Enterobacteriaceae
Fresh vegetables
mcr-1
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Summary:•Large-scale study showed high prevalence of mcr-1 in fresh vegetables in China.•Multiple mcr-1-positive E. coli isolates with different MLSTs were found in the same vegetable sample.•Dissemination of mcr-1 mediated by highly similar IncX4 or IncI2 plasmids.•IncHI2/ST3 plasmid carrying 14 resistance genes including mcr-1 was observed.•mcr-1-bearing plasmids from fresh vegetables similar to plasmids from clinical isolates/animals in various countries. The presence of mobilized colistin resistance (mcr) genes is a global concern. However, data concerning mcr in fresh vegetables, a reservoir for antibiotic resistance genes, are still rare. In this study, mcr genes were analysed in 528 vegetable samples from 53 supermarkets or farmer's markets in 23 cities of 9 provinces in China, and the mcr-positive Enterobacteriaceae were characterized. Nineteen (3.6%) samples carried one or more mcr-positive isolates, and the highest three detection rates were found in carrot, pak choi and green pepper. Twenty-four mcr-1-positive isolates (23 Escherichia coli and one Enterobacter cloacae) were obtained, and E. coli isolates showed high genetic diversity. Different multilocus sequence type (MLST) isolates were also observed within the same sample. All 24 isolates showed multidrug resistance, and 14 carried blaCTX-M genes. Most isolates harbored similarly conjugative IncX4-type (∼33 kb) or IncI2-type (∼60 kb) mcr-1-bearing plasmids. The sequenced prevalent IncX4 plasmid and IncI2 plasmid from tomato were similar to the relevant plasmids from animals and clinical isolates in various countries. mcr-1-bearing IncHI2/ST3 plasmid highly similar to that carrying 14 resistance genes from E. coli of chicken was also observed. In conclusion, a high prevalence of mcr-1 in fresh vegetables was found in China, and the dissemination of mcr-1 was mediated by similar IncX4 or IncI2 plasmids. The plasmids from vegetables showed high similarity to plasmids from clinical isolates, indicating MCR-1-producers in ready-to-eat vegetables may pose a huge threat to public health and measures need to be taken to ensure food safety.
ISSN:0924-8579
1872-7913
DOI:10.1016/j.ijantimicag.2019.04.013