Evaluation of Extended-Spectrum -Lactamases- ProducingIsolates of Salmonella spp. from Different Sources Using byPhenotypic andGenotypic Methods

Salmonella spp. are important zoonotic pathogens in humans and animals which cause salmonellosis. Use of uncontrolled antimicrobial agents in human and animal have been increased drug resistance in the different serotypes of Salmonella. The aim of this study was determining antibiotic resistant patterns and detection of ESBL producing isolates of Salmonellae spp. Isolated from different sources including human, poultry and cattle. A total of 70 salmonella isolates which obtained from Microbial Type Culture Collection of Microbiology department of Razi institute, Karaj-Iran, were subjected to determine of susceptibility testing to 30 antimicrobial agents. Phenotypic identification for ESBL producing isolates were analyzed by combined disk test (CT) according to CLSI guidelines. Genotypic characterization of isolates was performed by PCR based on blaSHV gene. (84.3%) of the Salmonella isolates were resistant to more than one antimicrobial agent. Thirty-two (45.7%) isolates was found to be multi-drug resistant (MDR) isolates that two of them were resistant to 13 antibiotics. The most common resistance to antibiotics was to cephalexin followed by to nitrofuratoin and tetracycline. No resistance was observed for amikacin, oflaxacin, enrofloxacin, cefotizoxim, cefotaxime, and imipenem. The results revealed that 10 isolates (14.3%) were ESBL producing isolates by combined disk test while only 6 isolates(8.6%) harbored the blaSHV gene.The results of this study showed the presence of resistance gene of blaSHV in different Salmonella spp. Isolated from livestock and poultry in Iran. Therefore the continuing monitoring and identification of ESBL producing isolates of Salmonella in the community is essential.