Background & objectives: Resistant microbial strains are a serious threat to public health in different societies. A mong the extended-spectrum β-lactamases (ESBL) producing strains the Enterobacteriaceae family which is considered as the main factors producing urinary tract infections, have created many problems in treatment of this kind of infections. This study was conducted to determine the frequency of β-lactamase TEM-1 gene in Enterobacteriaceae isolated from urine samples in Ardabil city.

  Methods: Within 6 months, 400 urinary isolates of Enterobacteriaceae of inpatients and outpatients were collected in Ardabil hospitals and were identified by standard methods. Antimicrobial susceptibility of isolates was tested by disk diffusion method, and ESBL producer confirmatory test was conducted using combined disk. Finally, the frequency of β-lactamase TEM-1 gene in producing extended-spectrum β-lactamases strains was investigated using PCR.

  Results: From 400 isolates of Enterobacteriaceae, 150 cases (37.5%) were ESBL producing. PCR results showed presence of the TEM-1 gene in 69 cases (46%). The frequency of this gene in isolates of Enterobacter (Aerogenes, Cloacae), Klebsiella (Pneumoniae, Oxytoca) and E. coli was obtained to be 62.5%, 54.5% and 44.8%, respectively. Proteus mirabilis and Serratia marcescens strains were lacking these genotypes.

  Conclusion: As regards the presence of TEM-1 gene, there is also increasing in other members of the Enterobacteriaceae family including Klebsiella and Enterobacter in addition to E. coli, therefore sufficient identification of this strains is necessary to prescribe the right medicine.