Phenotypic resistance and virulence gene profiles of non-typhoidal Salmonella in retail poultry products in Arusha, Tanzania: A One Health perspective

Résumé

Background and Aim: Non-typhoidal Salmonella (NTS) is a leading cause of foodborne illness, with poultry products serving as major transmission routes. In sub-Saharan Africa, surveillance of antimicrobial resistance (AMR) and virulence determi­nants remains limited. This study investigated the prevalence, AMR, and virulence gene profiles of NTS isolated from poultry products retailed in Arusha, Tanzania. Materials and Methods: A cross-sectional study was conducted between August and October 2023. A total of 240 samples (layer eggs and broiler meat) were collected from two wards in Arusha City using systematic random sampling. NTS isolates were confirmed by polymerase chain reaction (PCR) and tested for susceptibility to 11 antimicrobial agents using the Kirby–Bauer method. Virulence (invA and stn) and resistance genes (tetA, tetB, blaTEM, blaCTXM, and blaSHV) were screened by PCR. Statistical associations were analyzed using odds ratios (OR) and 95% confidence intervals (CI). Results: The overall prevalence of NTS was 23.3% (56/240). Layer eggs showed significantly higher contamination (20%) compared with broiler meat (3.3%) (OR = 10.0, 95% CI: 4.4–22.6, p < 0.001). Salmonella Typhimurium was the predomi­nant serotype. All isolates carried invA and stn genes. Alarmingly, 100% of isolates were resistant to imipenem (IMI), while resistance to ampicillin (58.9%) and tetracycline (41.1%) was also common. Multidrug resistance patterns were frequent, although resistance genes were detected at a low prevalence (tetA, 5.3%; blaTEM, 3.5%). Conclusion: The findings demonstrate a high prevalence of virulent and IMI-resistant S. Typhimurium in retail poultry prod­ucts in Arusha, particularly in eggs. These results highlight critical gaps in food safety regulation and antimicrobial steward­ship within the Tanzanian One Health framework. Further genomic studies are warranted to elucidate underlying resistance mechanisms and inform effective surveillance strategies. Keywords: antimicrobial resistance, non-typhoidal Salmonella, One Health, poultry, Tanzania, virulence genes.

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