Study of class 1 integrons and antibiotic resistance in Salmonella Typhimurium strains isolated from livestock and poultry

Evolution and dissemination of multidrug-resistant Salmonella enterica isolates have been reported. Resistance to antibiotic within Salmonella serotypes is a serious global concern. Integrons are genetic units that participate in capturing and dissemination of mobile gene cassettes among Gram-negative microorganisms. Integron mobility is facilitated by transposons and plasmids. Antibiotic resistance phenotype of 32 Salmonella enterica isolates of animal origin which were collected during 2011–2012 were investigated. All samples were assessed by culture method and standard biochemical tests for identification of Salmonella strains. After DNA extraction، the presence of class I integron was examined by PCR. The most common resistant phenotypes were to cefalothin (100%)، chloramphenicol (68/7%)، ampicillin (62/5%)، tetracycline (56/2%)، amoxicillin/ clavulanate (50%)، sulfamethoxazole (43/7%). Class 1 integrons were found in (55/5%) and (64. 2 %) of Salmonella isolates from livestock and poultry respectively. Discussion and Integron positive isolates had higher resistance to tetracycline، chloramphenicol، ampicillin sulfamethoxazole and amoxicillin / clavulanate compared with integron negative isolates. The ability of integrons to integrate resistance gene to antimicrobial agents makes them the main sources in the diffusion of antibiotic resistance.