ABSTRACT
Tetracyclines and sulfonamides are broad-spectrum antibacterial agents which have been used to treat bacterial infections for over half a century. The widespread use of tetracyclines and sulfonamides led to the emergence of resistance in a diverse group of bacteria. This resistance can be studied by searching for resistance genes present in the bacteria responsible for different resistance mechanisms. Salmonella is one of the leading bacteria causing foodborne diseases worldwide, and its resistance to tetracyclines and sulfonamides has been widely reported. The literature review searched the Virtual Health Library for articles with specific data in the studied samples: the resistance genes found, the primers used in PCR, and the thermocycler conditions. The results revealed that Salmonella presented high rates of resistance to tetracycline and sulfonamide, and the most frequent samples used to isolate Salmonella were poultry and pork. The tetracycline resistance genes most frequently detected from Salmonella spp. were tetA followed by tetB. The gene sul1 followed by sul2 were the most frequently sulfonamide resistance genes present in Salmonella. These genes are associated with plasmids, transposons, or both, and are often conjugative, highlighting the transference potential of these genes to other bacteria, environments, animals, and humans.
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.
