Prevalence and Antimicrobial Resistance of Salmonella spp., Shigella spp., and Listeria monocytogenes in Poultry Feeds and Ready-to-Eat Foods: A Farm-to-Fork Study in Conflict-Affected Maiduguri, Nigeria

Background Informal food supply chains in regions affected by conflict present significant risks associated with the transmission of foodborne pathogens and the development of antimicrobial resistance (AMR). The objective of this research is to investigate the prevalence and AMR patterns of Salmonella spp., Shigella spp., and Listeria monocytogenes in poultry feeds and ready-to-eat (RTE) foods available for sale in Maiduguri, located in northeastern Nigeria. Methods A cross-sectional survey was conducted involving the collection of 120 poultry feed samples and approximately 251 samples of RTE foods, with 120 samples specifically designated for the analysis of Listeria. Pathogen isolation was performed using standardized microbiological protocols (ISO/FDA-BAM), and the assessment of AMR was conducted utilizing the disk diffusion method in accordance with Clinical and Laboratory Standards Institute (CLSI) guidelines for Shigella (n=5), Salmonella (n=15), and Listeria (n=3) isolates. Prevalence rates were calculated with 95% confidence intervals derived from the Wilson score method. Results The study revealed a prevalence of Salmonella spp. at 10.0% (95% CI 5.8-16.8) in poultry feeds, with a maximum occurrence of 25.0% identified in the Monday Market, contrasting with a prevalence of 2.3% (0.8-6.7) reported in RTE foods, particularly in Bulumkutu fruits and meats from the Custom Market. Shigella spp. was identified in 3.33% (1.3-8.1) of feed samples and in 0.76% (0.1-4.2) of RTE foods, specifically within pineapple. L. monocytogenes was detected in 2.5% (0.8-7.1) of RTE foods, exclusively sourced from Baga Road market, including meat and sala sour milk. The isolates of Salmonella obtained from feeds demonstrated high levels of multidrug resistance (100% to tetracycline and 83.33% to fluoroquinolones), while Salmonella from RTE foods maintained resistance to tetracycline but exhibited a loss of resistance to fluoroquinolones. Notably, L. monocytogenes exhibited 100% resistance to both fluoroquinolones and cephalosporins while remaining sensitive to tetracycline. The presence of coliforms indicated inadequate hygiene conditions in the feeds, with 60.0% of samples showing contamination. Conclusion This initial study, which encompasses multiple pathogens within the conflict-affected region of Maiduguri, reveals significant upstream contamination of Salmonella in poultry feeds. It delineates the risks associated with ready-to-eat (RTE) foods and highlights the exclusive presence of L. monocytogenes in RTE products. Furthermore, the study indicates divergence in antimicrobial resistance (AMR) based on the food matrix. The findings underscore the urgent need for enhanced One Health surveillance, the implementation of improved hygiene practices in feed production, and the regulation of antimicrobial usage in informal poultry systems. Such measures are essential to effectively mitigate foodborne threats and the emergence of antimicrobial resistance in similarly underserved regions.