| Salmonella is one of the most important food-borne zoonotic pathogens.Pig is one of the main hosts of Salmonella,so pigs and pork positive for Salmonella had imposed a serious burden on animal husbandry and public health.China is the largest producing and consuming country of pork in the world.Guangdong and Hubei Provinces are the major pig-raising provinces,so the prevention and control of Salmonella contamination should be paid more attention in the production and processing of pork products.Due to the overuse and misuse of antimicrobials in animal breeding and veterinary practice,bacterial antimicrobial resistance becomes increasingly serious.This project aims to investigate the contamination and antimicrobial resistance of Salmonella in five slaughterhouses from Hubei or Guangdong province,and discuss the prevalence and transmission regulation of Salmonella contamination combined with previous studies by our group,so as to provide data support for the risk assessment and scientific management of Salmonella in pork production chain.The main results are as follows:1.Salmonella prevalence in five slaughterhouses from Hubei or Guangdong province in 2021From April to August in 2021,a total of 2640 samples were collected from five pig slaughterhouses from Hubei or Guangdong province,including rectal swab,carcass swab,pork and environmental samples,from which 302 Salmonella strains were identified with an overall prevalence of 11.44%.The prevalence was 14.86%(52/350),11.00%(88/800),and 2.98%(14/470)for the slaughterhouses A,B and C from Hubei province,respectively,16.31%(137/840)and 6.11%(11/180)for the slaughterhouses D and E from Guangdong province,respectively.Among the samples from different slaughter steps,the highest prevalence of Salmonella was in pork samples before precooling(24.71%,42/170)and after precooling(22.94%,39/170),followed by the samples of nasal swab(13.81%,58/420)and rectal swab(12.63%,125/990)of pigs in waiting lairage.The field positive rate of Salmonella in different farms was 81.82%(27/33),and the highest prevalence of Salmonella was the farm QYHG2.2.Antimicrobial resistance of Salmonella strains isolated in 2021A total of 155 strains of Salmonella strains isolated in 2021 were tested for susceptibility to 9 different antimicrobials using the micro-dilution broth method,and the results showed that the higher resistance proportions were in chloramphenicol(98.06%),florfenicol(96.77%),and gentamicin(90.32%),followed by ciprofloxacin(45.81%)and cefotaxime(12.26%),aztreonam(4.52%),meropenem(2.58%)and tigecycline(1.94%).All the strains were sensitive to polymyxin B.Using seven aztreonam-resistant strains and three tigecycline-resistant strains as donor bacteria,and Escherichia coli NK5449 as recipient bacterium,the conjugation transfer test was conducted by broth method,and the conjugates were screened by agar plate supplemented with the relative antimicrobial.The results showed that all the tigecyclineresistant strains were not transferred,while three out of the seven aztreonam-resistant strains exhibited the ability to conjugation transfer with the risk of horizontal resistance transmission.Furthermore,120 Salmonella strains isolated from Hubei province in 2019 were tested for susceptibility to aztreonam,tigecycline and polymyxin B.The results showed that the resistance proportion of Salmonella to aztreonam and tigecycline was 15.00% and 6.67%,respectively,higher than that of the strains isolated in 2021,and all the strains were also sensitive to polymyxin B. |
PDF Full Text Request