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ARS Home » Southeast Area » Athens, Georgia » U.S. National Poultry Research Center » Egg and Poultry Production Safety Research Unit » Research » Publications at this Location » Publication #424578
Research Project: Reduction of Foodborne Pathogens and Antimicrobial Resistance in Poultry Production Environments

Location: Egg and Poultry Production Safety Research Unit

Title: Prevalence, serotyping and antimicrobial resistance analysis of Salmonella isolated from the pastured poultry farm

Author
item KIM, MINHO - Oak Ridge Institute For Science And Education (ORISE)
item AL HAKEEM, WALID - Oak Ridge Institute For Science And Education (ORISE)
item CHUNG, TAEJUNG - Oak Ridge Institute For Science And Education (ORISE)
item Cho, Sohyun
item Li, Xiang
item ELLESTAD, LAURA - University Of Georgia
item REGMI, PRAFULLA - University Of Georgia
item Oladeinde, Adelumola
item Rothrock Jr, Michael

Submitted to: Poultry Science Association Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 5/1/2025
Publication Date: 6/1/2025
Citation: Kim, M., Al Hakeem, W., Chung, T., Cho, S., Li, X., Ellestad, L.E., Regmi, P., Oladeinde, A.A., Rothrock Jr, M.J. 2025. Prevalence, serotyping and antimicrobial resistance analysis of Salmonella isolated from the pastured poultry farm. Poultry Science Association Meeting Abstract. p. 513.

Interpretive Summary: Pastured poultry farms, managed without antibiotics, can provide a valuable baseline for studying Salmonella ecology and intrinsic antimicrobial resistance (AMR) profiles. This study investigated the impact of different broiler breeds on Salmonella prevalence and further characterized AMR and serotype distribution from 94 Salmonella isolates. Two different breeds, fast-growing Cornish Cross (CC) and slow-growing Freedom Ranger (FR), were used and samples were collected from broilers (ileum, ceca, fresh feces, feces collected from pasture, whole carcass rinses at processing (WCR)) and their environment (feed, water, flies and wild bird feces) at multiple time points from d3 post hatch through carcass processing (d56 and d77 for CC and FR, respectively). Salmonella prevalence was determined using traditional cultural methods with selective enrichment, and positive samples underwent whole-genome sequencing (WGS) and antimicrobial sensitivity testing (AST). One-way analysis of variance (ANOVA) and Tukey’s multiple comparison test were used to assess statistical differences in Salmonella prevalence between two breeds (a=0.05). Serotyping based on core genome multilocus sequence typing (cgMLST) was performed using the SISTR package and AST was performed using the CDC-NARMS protocol. Salmonella prevalence in CC (15.6%) was significantly higher than FR (7.5%, p<0.05), although Salmonella was only recovered from the WCR samples from the FR broilers. While low levels of Salmonella were recovered from water and wild bird feces samples (9.4% and 8.3%, respectively), flying insects was the greatest sampled environmental reservoir of Salmonella throughout the study (60%). WGS analysis identified 10 different serotypes including Bareilly (24.3%), Senftenberg (23.0%), Kentucky (20.3%), Typhimurium (9.5%), and Infantis (6.8%), with serotypes differences based on sample type and broiler breed. Even when raised without exogenous antibiotics, these isolates possessed resistances to various antibiotics with tetracycline and cefoxitin being most prevalent (42.6% and 26.6% of isolates, respectively). Multidrug resistance (MDR; =3 antibiotics) was observed from 20.2% of isolates, dominated by Senftenberg and Infantis (10 and 5 isolates, respectively), with >3 times more MDR isolates from CC compared to FR (11 and 3 NDR isolates, respectively). These findings demonstrate a significant breed effect on Salmonella prevalence and provide valuable insights into serotype and AMR diversity under a pastured poultry farming system, which can be critical for enhancing food safety and mitigating AMR risks for the poultry industry.

Technical Abstract: Pastured poultry farms, managed without antibiotics, can provide a valuable baseline for studying Salmonella ecology and intrinsic antimicrobial resistance (AMR) profiles. This study investigated the impact of different broiler breeds on Salmonella prevalence and further characterized AMR and serotype distribution from 94 Salmonella isolates. Two different breeds, fast-growing Cornish Cross (CC) and slow-growing Freedom Ranger (FR), were used and samples were collected from broilers (ileum, ceca, fresh feces, feces collected from pasture, whole carcass rinses at processing (WCR)) and their environment (feed, water, flies and wild bird feces) at multiple time points from d3 post hatch through carcass processing (d56 and d77 for CC and FR, respectively). Salmonella prevalence was determined using traditional cultural methods with selective enrichment, and positive samples underwent whole-genome sequencing (WGS) and antimicrobial sensitivity testing (AST). One-way analysis of variance (ANOVA) and Tukey’s multiple comparison test were used to assess statistical differences in Salmonella prevalence between two breeds (a=0.05). Serotyping based on core genome multilocus sequence typing (cgMLST) was performed using the SISTR package and AST was performed using the CDC-NARMS protocol. Salmonella prevalence in CC (15.6%) was significantly higher than FR (7.5%, p<0.05), although Salmonella was only recovered from the WCR samples from the FR broilers. While low levels of Salmonella were recovered from water and wild bird feces samples (9.4% and 8.3%, respectively), flying insects was the greatest sampled environmental reservoir of Salmonella throughout the study (60%). WGS analysis identified 10 different serotypes including Bareilly (24.3%), Senftenberg (23.0%), Kentucky (20.3%), Typhimurium (9.5%), and Infantis (6.8%), with serotypes differences based on sample type and broiler breed. Even when raised without exogenous antibiotics, these isolates possessed resistances to various antibiotics with tetracycline and cefoxitin being most prevalent (42.6% and 26.6% of isolates, respectively). Multidrug resistance (MDR; =3 antibiotics) was observed from 20.2% of isolates, dominated by Senftenberg and Infantis (10 and 5 isolates, respectively), with >3 times more MDR isolates from CC compared to FR (11 and 3 NDR isolates, respectively). These findings demonstrate a significant breed effect on Salmonella prevalence and provide valuable insights into serotype and AMR diversity under a pastured poultry farming system, which can be critical for enhancing food safety and mitigating AMR risks for the poultry industry.