Background: Beta- lactamase enzymes are the most important resistant factors to beta lactam antibiotics among gram negative bacteria. Nowadays, the prevalence of beta- lactamase infection is increasing worldwide and drawn the scientists attention as an important subject. Due to high prevalence of bacteria contained TEM beta lactamase and AmpC enzymes, using molecular methods especially designing universal primers could be valuable to detect all of them. The aim of this study was to determine the prevalence of TEM and AmpC (Dha and MOX) beta- lactamase genes using universal primers.

Methods: A total of 500 clinical specimens from various Hospitals in Tehran, Iran were collected and analyzed for E. coli based on biochemical tests. These clinical specimens were also screened by Disk diffusion agar, combined disk method and PCR to detect the samples producing extended- spectrum beta- lactamase.

Results: Overall 200 isolates of Escherichia coli were collected from the 500 clinical specimens out of which 128(64%) isolates were positive by PCR assay and showed bla- TEM, bla- AmpC (Dha, MOX) genes, 74(57.8%) and 5(3.9%) to have bla- TEM and bla Dha, respectively. Mox gene was not detected in any of the specimens.

Conclusions: Our results revealed that using the molecular methods with phenotype methods is very essential for complete detection of Beta- lactamases. There is the need for updating the treatment protocol because the prevalence of this resistance is increasing.