Species diversity and antimicrobial resistance of Salmonella detected in pork and chicken in Yuyao, Zhejiang

  Objective  To understand the distribution and pollution of Salmonella in pork and chicken in Yuyao, Zhejiang.

  Methods  A total of 206 fresh pork and chicken samples were collected from major shopping malls and farm produce markets in Yuyao between June 2019 and October 2020, and then the enrichment, isolation, biochemical identification, serotyping and drug sensitivity test were conducted.

  Results  In 61 chicken samples and 145 pork samples, 25 and 68 were positive for Salmonella, respectively. The positive rates were 40.98% and 46.90% . A total of 117 strains of Salmonella belonging to 17 serotypes were isolated from 93 meat samples, including 89 strains from pork samples and 28 strains from chicken samples. S. derby (30/89, 33.71%), S. london (15/89, 16.85%), S. rissen (14/89, 15.73%) and S. typhimurium (13/89, 14.61%) were the predominant serotypes in pork samples. However, S. enteritidis (9/28, 32.14%), S. kentucky (6/28, 21.43%), and S. typhimurium (4/28, 14.29%) were most commonly detected in chicken samples. Severe antibiotic resistance to penicillins, tetracyclines and folate pathway antagonists were detected. The resistance rates to ampicillin, piperacillin and tetracycline and compound sulfamethoxazole were 79.49%, 52.14%, 74.36% and 56.41%, respectively. A total of 71 multidrug-resistance (MDR) strains were detected, and 41 strains, including 29 strains from pork samples and 12 strains from chicken samples, showed multi resistance to ampicillin, chloramphenicol, streptomycin, sulfamethoxazole and tetracycline (ACSSuT). There were 11 extended-spectrum β-lactamases (ESBLs) producing strains, accounting for 9.40%, including 5 strains from pork samples (5.62%, 5/89) and 6 strains from chicken samples (21.43%, 6/28).

  Conclusion  This study indicated that the detection rate of Salmonella was high in chicken and pork samples in Yuyao. The isolates belonged to multi serotypes and showed high multidrug-resistance rate and complicated resistance mechanism. Therefore, it is necessary to strengthen the daily meat monitoring and analysis to provide evidence for the timely intervention to reduce transmission of Salmonella to humans through food chain.