Drug resistance and homology of diarrheagenic Escherichia coli from livestock and poultry meats in markets in Shaoxing, Zhejiang, 2021−2022

Objective  To explore the drug-resistance phenotype and homology of diarrheagenic Escherichia coli (DEC) isolated from livestock and poultry meats in Shaoxing, Zhejiang province, from March 2021 to November 2022.

Methods A total of 420 livestock and poultry meat samples were collected from farm produce markets, supermarkets and restaurants in Shaoxing during 2021−2022 for DEC isolation and identification. The drug susceptibility tests to 13 kinds of antibiotics were conducted for the isolates by micro broth dilution method. The molecular typing of the isolates was performed by pulsed-field gel electrophoresis (PFGE) and the clustering analysis was performed with software BioNumerics 7.6.

Results In 420 livestock and poultry meat samples, 72 were positive for DEC, the positive rate was 17.14% (72/420). In 112 livestock meat samples and 308 poultry meat samples, 22 and 50 were positive for DEC, respectively. The positive rates were 19.64% and 16.23%. A total of 77 strains of DEC were isolated, including 24 strains from livestock meat and 53 from poultry meat. The 77 strains of DEC could be classified into three types, including 71 strains of enteroaggregative Escherichia coli (EAEC) (92.21%), 4 strains of enteropathogenic E. coli (EPEC) (5.19%), 2 strains of Shiga toxin-producing E. coli (STEC) (2.60%). The resistance rate to tetracycline was highest (76.62%, 59/77), and the resistance rates to ampicillin, chloramphenicol, trimethoprim/sulfamethoxazole were 67.53% (52/77), 61.04% (47/77) and 57.14% (44/77), respectively. One EAEC strain was found to be resistant to carbapenems (imipenem). Forty-six drug resistance spectrums were found in the 77 strains, and multi-drug resistance strains accounted for 70.13% (54/77). The resistance rates of poultry meat strains to cefzaolin (χ²=9.403, P=0.002), cefotaxime (χ²=7.721, P=0.005), gentamicin (χ²=11.422, P<0.001), nalidixicacid (χ²=10.685, P=0.001) and ciprofloxacin (χ²=6.340, P=0.012) were higher than those of livestock meat isolates, the differences were significant . The multi-drug resistant rate (≥5 classes) in poultry meat strains was higher than that in livestock meat strains, the difference was significant (χ²=7.423, P=0.006). Using pulsed field gel electrophoresis (PFGE), 76 strains of DEC were divided into 75 band types and 72 band clusters. 70 strains of EAEC were divided into 69 band types and 66 band clusters. 4 strains of EPEC were divided into 4 band types and 4 band clusters and 2 strains of STEC were divided into 2 band types and 2 band clusters.

Conclusion The predominant type of DEC isolated from livestock and poultry meat in Shaoxing was EAEC. The resistance rate of the isolates to common drugs was high, and the drug resistance spectrum was wide. The prevalence multi-drug resistance was common. The PFGE band type of the isolates showed polymorphism distribution and low genetic relationship. It is necessary for animal husbandry to strengthen the management of the use of antibiotics and improve drug resistance surveillance to prevent and control the spread of drug-resistant DEC.