Retail fish markets in Bangladesh are hidden hotspots of multidrug resistant Salmonella providing critical One Health insights

Salmonella spp., a major foodborne pathogen, is frequently detected in fish, seafood. They can harbour multidrug-resistant (MDR) strains with various resistant genes, posing serious public health risks through their transmission. Mobile genetic elements (MGEs) such as Class 1 integron plays a major role in resistant genes transfer to ensure rapid evolution of bacteria. In Bangladesh, fishes such as Tilapia, Rui, and Pangas are commonly consumed, although there is information on Salmonella spp. and their resistant pattern in different fishes, however no information is available on how this bacterium transfer resistant genes in association with Class 1 integron in Bangladesh. A cross-sectional study was conducted in fish markets of Savar upazila of Dhaka and Sadar upazila of Manikganj districts, Bangladesh, from March to August 2025. A total of 342 fish samples we collected and Salmonella spp. was detected using the culture method, VITEK-2 system and PCR. Antimicrobial susceptibility was assessed for 12 clinically relevant antibiotics using the disc diffusion method according to CLSI guidelines, and isolates were categorized as MDR, XDR, or PDR. PCR was further employed to screen for antibiotic resistance genes and Class 1 integron. Statistical analyses were conducted using R programming language. Salmonella spp. was detected in 47.4% of fish samples (95% CI 42.1–52.7), with the highest prevalence in Rui (78.9%; 95% CI 70.6–85.4), followed by Pangas (32.5%; 95% CI 24.6–41.5) and Tilapia (30.7%; 95% CI 23.0–39.7). Location wise distribution showed that Savar upazila had 46.8% (95% CI 39.5–54.3) prevalence of Salmonella spp., while Sadar upazila of Manikganj had 48.0% (95% CI 40.6–55.4). Antimicrobial susceptibility testing revealed high resistance to ampicillin (66.7%) and tetracycline (48.1%). MDR strains accounted for 42.6% of isolates (95% CI 35.2–50.3), predominantly in Rui (53.3%). Class 1 integron was present in 18.5% of isolates (95% CI 13.3–25.2), mainly in Tilapia (48.6%) and Pangas (27.0%), with sul-1 (5.6%; 95% CI 2.9–10.2) and sul-3 (14.8%; 95% CI 10.2–21.1) genes identified. Nearly half of the sampled fish harboured Salmonella spp., with a substantial proportion being MDR with the presence of Class 1 integron and sulfonamide-resistance genes. The association between Class 1 integrons and selected resistance determinants suggests the potential involvement of mobile genetic elements in antimicrobial resistance dissemination. However, direct transmission pathways and resistance mechanisms were not investigated in this study. Nevertheless, the findings indicate potential public health concerns and highlight the need for continued surveillance and improved antimicrobial stewardship. These findings underscore the need for regular monitoring, prudent antibiotic use in aquaculture, and improved food safety measures.