Tetracycline Resistance in Salmonella spp. and Escherichia coli from Brazilian Poultry

ABSTRACT Antimicrobial resistance (AMR) is a pressing global public health issue, driven by the widespread use of antibiotics in both human and veterinary medicine. Tetracyclines, widely used in livestock for growth promotion and disease treatment, have contributed significantly to the emergence of resistant bacterial strains. This study aimed to evaluate the tetracycline resistance profiles of Salmonella spp. and Escherichia coli isolates from the poultry supply chain in Brazil, and identify the primary tetracycline resistance genes involved. A total of 97 Salmonella strains and 195 E. coli strains were analyzed for tetracycline resistance using the disc diffusion method and PCR to detect resistance genes (tetA, tetB, tetC, tetD, tetE, and tetG). The results revealed high tetracycline resistance rates, with 88.66% of Salmonella strains carrying the tetA gene, 4.12% harboring tetB and 1.03% carrying tetD. Among E. coli isolates, 64.62% carried tetA, 65.13% carried tetB, and 43.59% exhibited both genes. The tetE gene was detected in 1.03% of E. coli strains. These findings highlight the widespread presence of tetracycline resistance determinants in poultry-associated bacteria, underscoring the need for stricter antimicrobial use regulations and enhanced AMR monitoring in animal production systems to mitigate public health risks.