Epidemic characteristics and molecular transmission mechanism of mcr-1-carrying Escherichia coli isolates from food animal-derived in Hanzhong, Shaanxi Province
- Author:
TAO Junqi
;
WENG Rui
;
HOU Xuan
- Publication Type:Journal Article
- Keywords:
Escherichia coli;
animal-derived;
food;
mcr-1;
colistin;
multidrug-resistant
- From:
China Tropical Medicine
2024;24(11):1312-
- CountryChina
- Language:Chinese
-
Abstract:
Objective To investigate the epidemiological characteristics and molecular transmission mechanism of the colistin resistance gene mcr-1 in food animal-derived Escherichia coli in Hanzhong, Shaanxi Province, and to grasp the prevalence of mcr-1 positive Escherichia coli in Hanzhong, in order to offer the empirical evidence for the prevention and management of disseminating the mcr-1 colistin resistance gene in both community and hospital settings. Methods From November 2019 to May 2020, frozen whole chicken carcasses and frozen raw ground pork were randomly sampled from seven major supermarkets in Hanzhong, Shaanxi Province, for the isolation and identification of Escherichia coli. The mcr-1 gene was detected using PCR analysis, and the drug susceptibility of mcr-1-positive strains was assessed using the broth dilution method. Whole genome sequencing, S1-pulsed field gel electrophoresis (PFGE), and Southern blot were used to locate the mcr-1 gene. Results Out of 159 samples randomly collected from seven different supermarkets, 77 Escherichia coli strains were isolated, and 11 strains carrying the mcr-1 gene were detected, with a positive rate of 14.29%. All 11 mcr-1-positive strains were multidrug-resistant, with a minimum inhibitory concentration (MIC) for colistin ≥2 mg/L (11/11). They exhibited a 100.00% resistance rate to ampicillin, streptomycin, tetracycline, and chloramphenicol (11/11), and all produced extended-spectrum beta-lactamases (ESBLs). The strains exhibited susceptibility to carbapenems and cefoxitin but had a 90.91% resistance rate to quinolones ciprofloxacin and levofloxacin. The mcr-1 gene was located on plasmids in 10 of the mcr-1-positive strains, with plasmid sizes approximately 60 kb and 220 kb. The 11 mcr-1-positive Escherichia coli strains belonged to 9 different sequence types (STs), including one previously unidentified ST. Besides carrying the colistin resistance gene mcr-1, all isolates possessed at least one ESBLs gene, predominantly blaCTX-M-55 (8/11, 72.73%). The plasmid types harboring mcr-1 were predominantly IncI2 (5/11, 45.45%) and IncHI2 (5/11, 45.45%), with one strain having mcr-1 located on the chromosome. Conclusions The mcr-1-positive Escherichia coli detected in this study are all multidrug-resistant and produce ESBLs, predominantly blaCTX-M-55. The mcr-1 gene can be transmitted through plasmid and chromosome.
- Full text:20251112100058149444.Epidemic characteristics and molecular transmission mechanism of mcr-1-carrying Escherichia coli isolates from food animal-derived in Hanzhong, Shaanxi.pdf
