Prevalence and Antimicrobial Resistance of Salmonella spp. in Aquacultured Nile Tilapia (Oreochromis niloticus) Commercialized in Federal District, Brazil.

Abstract

This study aimed to assess Salmonella spp. prevalence in aquaculture Nile tilapia commercialized in the Federal District, Brazil, and determine the antimicrobial resistance profile of the isolates. Fifty-seven Salmonella spp. strains were isolated from 101 samples of fresh tilapia fillets collected in the Federal District, Brazil. These isolates were subjected to antimicrobial susceptibility testing by the Kirby-Bauer disk diffusion method and analyzed for the presence of blaCTX, tetB, sul2, and floR resistance genes. The Salmonella spp. prevalence in fresh tilapia fillets was 45.5%; that is, 46 of 101 samples were positive for the InvA gene. The antimicrobial resistance profile showed high resistance rates for amoxicillin/clavulanic acid (87.7%), tetracycline (82.5%), sulfonamide (57.9%), and chloramphenicol (26.3%). Additionally, 56.1% of Salmonella spp. isolates were multidrug-resistant (MDR) isolates. The beta-lactam-resistant gene blaCTX was identified in 66.7% of isolates, the tetracycline resistance gene tetA in 54.4%, and the chloramphenicol resistance gene floR in 50.9%, while the sulfonamide resistance gene sul2 was present in 49.1%. The results revealed that tilapia fillets were highly contaminated with MDR Salmonella. These Salmonella spp. strains carried multiple antimicrobial resistance genes, which might facilitate their dissemination to consumers along the production chain. Hence, there is an evident need to control Salmonella in fish production systems to ensure public health.