Background: Nowadays, the widespread use of broad-spectrum beta-lactam antibiotics has increased antibiotic resistance around the world. The aim of this study was to assess and identify genes bla_TEM, bla_SHV, bla_oxa and bla_aada in clinical isolates E.coli by Multiplex- PCR methods.

Materials and methods: In this descriptive study, 150 stool samples from different treatment centers in Tehran were randomly gathered; and biochemical tests detected 55 E. coli. Antimicrobial susceptibility testing was performed by disk diffusion method according to CLSI. Multiple PCR assay was used to identify the genes β-lactamase. Data were analyzed by descriptive statistical analysis using SPSS version 19.

Results: Highest sensitivity was observed to cefpodoxime and trimethoprim (90.9% and 58.1% respectively) and the maximum resistance was reported to imipenem and ciprofloxacin (76.3% and 100% respectively). PCR results showed bla _oxa gene in 40 isolates (72.7%), aadA gene in 15 samples (27.2%) and concurrent  bla_oxa/ aadA genes in 12 isloates (21.8%). bla_TEM and bla_SHV genes were not identified in samples.

Conclusion: Antibiotic resistance to E.coli in children with diarrhea is indicated the indiscriminate use of antibiotics. Monitoring and control of drug-resistant intestinal bacteria play a major role in preventing the creation of resistant strains.

Keywords: Escherichia coli, Extended specterum β- lactamases, Multiplex-PCR.