Zhongguo shipin weisheng zazhi (Dec 2023)
Monitoring and analysis of STEC in cow manure from a dairy farm and retail fresh beef around Chengdu City
Abstract
ObjectiveTo understand the carrying status and strain characteristics of STEC strains in cattle and beef in the local area， provide scientific basis for evaluating the STEC pollution status， infection risk， prevention and control strategies in the region， the Shiga toxin producing Escherichia coli （STEC） in the feces of calves and adult cows and feeding environment in a dairy farm around Chengdu， as well as fresh beef from vegetable markets and supermarkets for three years were continuously monitored.MethodsSTEC using fluorescence quantitative PCR method was identified， and drug sensitivity testing using micro broth dilution method was conducted. After sequencing the entire genome of the isolated strain， the MLST type， strain type， serotyping， and virulence gene information were obtained on the EnteroBase database. The stx subtype information was compared using the Abricate software. Perform cgMLST clustering analysis was used by BioNumerics 7.6 software.ResultsFrom 2019 to 2021， a total of 247 cow manure and environmental samples were collected from dairy farms， and 25 STEC strains were isolated， with a detection rate of 10.12%. 294 fresh beef samples were collected and 32 STECs were isolated， with a detection rate of 10.88%. A total of 57 STEC strains were isolated. The STEC strain had the highest resistance rate to ampicillin， reaching 42.11%（24/57）， followed by cefotaxime and cefazolin at 38.60%（22/57）. Multiple resistant strains accounted for 35.09%（20/57）. A total of 30 serotypes were isolated from 57 STEC strains， among which the serotypes that can cause outbreaks include O26：H11， O103：H25， and O145：H12. Through virulence gene analysis， it was found that subtypes with pathogenic risk included stx2a， stx2c， stx2d， stx2e， stx2g， stx2k， as well as eae-STEC and STEC/ETEC heterozygous strains.ConclusionThe pollution of STEC in cow manure from dairy farms and fresh beef from vegetable markets continued to exist from 2019 to 2021. The detection rate of calf feces was 21.43%， which was higher than that of adult cow feces by 0.91%. The STEC detection rate of fresh beef in vegetable markets is significantly higher than that in supermarkets. The drug resistance of strains isolated from cow manure is more severe than that of strains isolated from beef. Some isolated strains have stronger pathogenicity due to carrying strong virulence genes or other pathogenic related genes.
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