Molecular detection of class 1, 2 and 3 integrons and some antimicrobial resistance genes in Salmonella Infantis isolates

Background and Objectives: Multidrug resistant Salmonella strains have been observed around the world in recent years. Many mechanisms contribute to the spread of antimicrobial resistance genes. This study aimed at determining the distribution and transmission of class 1, 2 and 3 integrons among MDR Salmonella isolates collected from a selection of chicken broilers in the north of Iran. Materials and Methods: PCR assays were used to detect genes for tetracyclines (tetA, tetB and tetG), chloramphenicol (cat1 and floR), and streptomycin (strA). Also, the presence of class 1, 2 and 3 integrons in all MDR isolates was evaluated using specific primers for the integrase genes of integrons intI1, intI2 and intI3. Results: Class 1, 2 and 3 integrons were present in 36%, 42% and 4% of the MDR isolates, respectively. Out of the tetracyclines resistant isolates, 47 (100%) and 5 (10.6%) carried tetA, tetB genes, respectively, while no isolate was positive for the tetG gene. All 36 chloramphenicol- resistant strains carried floR and cat1 genes. Nine (18%) Salmonella Infantis isolates harbored the strA gene, conferring resistance to sterptomycin. Conclusion: This study found a high frequency of antimicrobial resistance genes among Salmonella isolates; therefore, management strategies are needed to prevent food-borne diseases caused by MDR Salmonella from food supplies.