Prevalence of Tetracycline Resistance Genes among Clinical Isolates of Salmonella enterica

Aims The use of antibiotics in food-producing animals has elevated concerns regarding their potential affect on human health. Resistant Salmonella may be transmitted through the food chain to humans. The aim of this study was to determine the prevalence of tetracycline resistance genes among tetracycline-resistant Salmonella enterica from Iran. Materials & Methods In this experimental study, A total of 4369 stool specimens were collected via rectal swab from hospitalized children under the age of 5 with watery diarrhea, with or without blood, mucus and stomach cramps. Antimicrobial susceptibility profiles of Salmonella isolates were performed and Minimum inhibitory concentration (MIC) of tetracycline was assessed. Bacteria were grown on blood agar at 37°C overnight, and genomic DNA was extracted. For evaluating of PCR products used of 1.5% agarose gel in TBE buffer at for 80min. Findings High level of resistance was observed against minocycline (78.5%), tetracycline (76.0%), nalidixic acid (66.6%) and streptomycin (42.0%). The MIC for 46.0% of the isolates was 256μg/ml, while 15.6% showed the MIC of 128μg/ml and the remaining revealed 64μg/ ml MIC to tetracycline. Among the 33 tetracycline-resistant isolates the tet(A) or tet(B) genes were detected in 10 (23.8%) and 5 isolates (11.9%), respectively. The tet(A)and tet(B) genes were identified in 2 out of the 42 tetracycline-resistant Salmonella isolates (4.8%). The tet(C) or tet(D)genes were not found among tetracycline-resistant isolates. Conclusion Resistance to Salmonella strains is increasing. The predominant tetracyclineresistant gene is tet(A) followed by tet(B).