期刊
ANTIMICROBIAL RESISTANCE AND INFECTION CONTROL
卷 6, 期 -, 页码 -出版社
BIOMED CENTRAL LTD
DOI: 10.1186/s13756-017-0250-8
关键词
Colistin; Mcr-1; Plasmid; ISApl1
类别
资金
- Swiss Federal Office of Public Health, Division Communicable Diseases
Background: Mcr-1-harboring Enterobacteriaceae are reported worldwide since their first discovery in 2015. However, a limited number of studies are available that compared full-length plasmid sequences of human and animal origins. Methods: In this study, mcr-1-bearing plasmids from seven Escherichia coli isolates recovered from patients (n = 3), poultry meat (n = 2) and turkey meat (n = 2) in Switzerland were further analyzed and compared. Isolates were characterized by multilocus sequence typing (MLST). The mcr-1-bearing plasmids were transferred by transformation into reference strain E. coli DH5 alpha and MCR-1-producing transformants were selected on LB-agar supplemented with 2 mg/L colistin. Purified plasmids were then sequenced and compared. Results: MLST revealed six distinct STs, illustrating the high clonal diversity among mcr-1-positive E. coli isolates of different origins. Two different mcr-1-positive plasmids were identified from a single E. coli ST48 human isolate. All other isolates possessed a single mcr-1 harboring plasmid. Transferable IncI2 (size ca. 60-61 kb) and IncX4 (size ca. 33-35 kb) type plasmids each bearing mcr-1 were found associated with human and food isolates. None of the mcr-1-positive IncI2 and IncX4 plasmids possessed any additional resistance determinants. Surprisingly, all but one of the sequenced mcr-1-positive plasmids lacked the ISApl1 element, which is a key element mediating acquisition of mcr-1 into various plasmid backbones. Conclusions: There is strong evidence that the food chain may be an important transmission route for mcr-1-bearing plasmids. Our data suggest that some epidemic plasmids rather than specific E. coli clones might be responsible for the spread of the mcr-1 gene along the food chain.
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