Phenotypic characteristics and genotypic correlation of antimicrobial resistant (AMR) Salmonella isolates from a poultry slaughterhouse and its downstream retail markets

Abstract

The present study investigated the distribution, antimicrobial susceptibility profiles, serotypes and genotypes of Salmonella isolates from a slaughterhouse (including lairage and slaughter line) and its downstream retail markets to determine the main sources of Salmonella contamination in retail chicken meat. Positive identification rates in the slaughterhouse and retail markets were 9.5% (81/852) and 41.8% (69/165), respectively. Among the Salmonella serovars identified, S. Albany was the most prevalent but other serovars including S. Montevideo and S. Virchow were also present prominently. Antimicrobial susceptibility testing revealed that the highest antimicrobial resistance rate was against nalidixic acid (139/150, 92.7%), that 56.7% (85/150) isolates were multidrug-resistant (MDR), and that the resistance profile of 20.7% (31/150) isolates was ACSSuT (ampicillin, chloramphenicol, streptomycin, sulfonamides and tetracycline). Ten virulence genes were detected in 69 isolates from retail chicken meat; the Salmonella pathogenicity island genes invA, hilA, sipA, sopB, sopD, ssrA, and ssaR were present in most of the isolates (94.2%–100%). Based on analysis of pulsed-field gel electrophoresis (PFGE) results, our findings indicated that MDR isolates could be transmitted from slaughterhouse to its downstream retail markets. In addition, the present study indicates three possible routes of Salmonella contamination in retail chicken meat, including initial presence, cross-contamination from carrier broilers slaughtered on the same day, and contamination from resident flora in slaughterhouse, with the last route being the most common in the present study.