Abstract
Monitoring antimicrobial resistance of foodborne pathogens in poultry is critical for food safety. We aimed to compare antimicrobial resistance phenotypes in Salmonella isolated from poultry samples as influenced by isolation and antimicrobial susceptibility testing methods. Salmonella isolates were cultured from a convenience sample of commercial broiler ceca with and without selective broth enrichment, and resistance phenotypes were determined for 14 antimicrobials using the Sensititre® platform and a qualitative broth breakpoint assay. The broth breakpoint method reported higher resistance to chloramphenicol, sulfisoxazole, and the combination of trimethoprim and sulfamethoxazole, and lower resistance to streptomycin as compared to the Sensititre® assay in trial one. Selective enrichment of samples containing Salmonella in Rappaport-Vassiliadis broth reported lowered detectable resistance to amoxicillin/clavulanic acid, ampicillin, azithromycin, cefoxitin, ceftriaxone, nalidixic acid, and meropenem, and increased resistance to streptomycin and tetracycline than direct-plating samples in trial one. Using matched isolates in trial two, the Sensititre® assay reported higher resistance to chloramphenicol and gentamicin, and lower resistance to nalidixic acid as compared to the broth breakpoint method. These results suggest methodology is a critical consideration in the detection and surveillance of antimicrobial resistance phenotypes in Salmonella isolates from poultry samples and could affect the accuracy of population or industry surveillance insights and intervention strategies.
Highlights
Salmonella is one of the most common foodborne pathogens
While the broth breakpoint method does not produce minimum inhibitory concentration (MIC). Data, both methods can be compared to estimate resistance prevalence using the current breakpoint concentrations. We proposed that this broth breakpoint method, facilitating more isolates to be tested, was a more representative means of evaluating phenotypic antimicrobial resistance (AMR) patterns from a food animal population where foodborne pathogens, such as Salmonella, are expected to be found in much higher prevalence and concentration with greater diversity
From the above positive samples, a total of 1748 Salmonella isolates collected from 20 direct plating samples were processed by the broth breakpoint assay and 55 isolates from 20 direct plating samples were analyzed by the Sensititre® method
Summary
Salmonella is one of the most common foodborne pathogens. The intestinal tract of poultry and other food animals is considered the main foodborne Salmonella reservoir [1,2].An increasing incidence of antimicrobial resistance (AMR) has been reported in poultrySalmonella isolates where antibiotics are extensively used in production systems [3,4]. The intestinal tract of poultry and other food animals is considered the main foodborne Salmonella reservoir [1,2]. An increasing incidence of antimicrobial resistance (AMR) has been reported in poultry. The link between antimicrobial usage in food animals and clinical treatment failures in human salmonellosis cases remains controversial and inconclusive, the United States. Poultry Salmonella isolates carrying AMR genes have the potential to pass to consumers along the farm-to-fork continuum [6]. Those resistant Salmonella isolates could threaten public health when their resistance phenotypes interfere with drug
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