Introduction & Objective: TEM-1 beta lactamase gene is one of the important plasmidic genes in Enterobacteriaceae which is the cause of over 90% of Escherichia coli isolates resistance to beta lactam antibiotics. In this study, the frequency of TEM-1 gene in nosocomial strains of Escherichia coli, Klebsiella pneumoniae and Enterobacter was investigated using PCR.

Materials & Methods: In this descriptive -analytical study, 83 ESBLs producing enteric bacteria (Escherichia coli, Klebsiella pneumoniae and Enterobacter strains) isolated from hospital clinical samples were studied for the presence of TEM-1 gene using TEM-1 beta lactamase specific primers (Gene-Fanavaran,Iran) using PCR. The detection of 1079 bp bands in poly acrylamide gel electrophoresis was considered as presence of TEM-1 gene in bacterial isolates. Data were analyzed using Chi-Square test.

Results: TEM-1 gene was detected in 54.2% (45) of isolated bacteria. The frequency of TEM-1 gene in different isolates was not significant. TEM-1 gene was detected in 62.5 % 0f Enterobacter, 58.3% of K.pneumoniae and 48.7% of E.coli isolates.

Conclusion: This study showed that, TEM-1 gene encodes over 50% of ESBLs in enteric bacteria. Therefore, we recommend detection of this gene as a routine bacteriologic procedure in management of the nosocomial infections caused by enteric bacteria.