Determination of antimicrobial resistance patterns in Salmonella from commercial poultry as influenced by microbiological culture and antimicrobial susceptibility testing methods

Authors: WANG, XI - Texas A&M University; CHANEY, EVAN - Diamond V Mills, Inc; PAVLIDIS, HILARY - Diamond V Mills, Inc; MCGINNIS, JAMES - Diamond V Mills, Inc; Byrd Ii, James - Allen; FARNELL, YUHUA - Texas A&M University; JOHNSON, TIMOTHY - Diamond V Mills, Inc; MCELROY, AUDREY - Texas A&M University; FARNELL, MORGAN - Texas A&M University

Submitted to: Microorganisms
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/12/2021
Publication Date: 6/17/2021
Citation: Wang, X., Chaney, E.W., Pavlidis, H.O., Mcginnis, J.P., Byrd II, J.A., Farnell, Y.Z., Johnson, T.J., Mcelroy, A.P., Farnell, M.B. 2021. Determination of antimicrobial resistance patterns in Salmonella from commercial poultry as influenced by microbiological culture and antimicrobial susceptibility testing methods. Microorganisms. 9(6). Article 1319. https://doi.org/10.3390/microorganisms9061319.
DOI: https://doi.org/10.3390/microorganisms9061319

Interpretive Summary: The aim of the study was to compare an automated antibiotic resistance detection system and an assay to evaluate a food safety bacterium, Salmonella, and the antibiotics they are resistant to in food safety systems. Salmonella recovered from part of the gastrointestinal tract from meat-type chickens were analyzed for their antibiotic resistance patterns using different culture methods. Resistance to 14 different antibiotics were tested using an automated system, Sensititre®, and a high number of bacteria detection assay (high-throughput breakpoint assay). The high-throughput breakpoint method resulted in higher resistance to the antibiotics chloramphenicol, sulfisoxazole, and the combination of trimethoprim and sulfamethoxazole resistance, and lower resistance to streptomycin as compared to the Sensititre® method. A method that improves the growth of Salmonella (Rappaport-Vassiliadis broth) lowered resistance to the antibiotics amoxicillin/clavulanic, ampicillin, azithromycin, cefoxitin, ceftriaxone, nalidixic acid, and meropenem, and increased resistance to streptomycin and tetracycline. The high-throughput breakpoint assay, which tests more bacterial isolates, leads to different antibiotic resistance patterns in poultry Salmonella. Enriching the culture method for Salmonella using Rappaport-Vassiliadis broth might have a selective for different antibiotic resistance patterns. These results suggest more Salmonella isolates should be tested for a more accurate representation of poultry population.

Technical Abstract: Monitoring antimicrobial resistance of foodborne pathogens in poultry is critical for food safety. A comparison was done on 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.