Introduction and Objectives: Enterobacteriaceae are the largest and the most diverse family of Gram-negative bacteria in medicine. These bacteria can cause more than 70% urinary tract infections (UTI). Lactam antibiotics families are the first choice in the treatment of infections caused by pathogenic Escherichia coli strains.The present study was designed to determine the antimicrobial susceptibility pattern of E.coli isolated from urine culture of patients admitted to several hospitals and laboratories in Mashhad. Materials and Methods: One hundred of Escherichia coli isolates from patients (50 samples from patients in laboratories and 50 samples from hospitalized patients) with urinary tract infection producing broad-spectrum beta-lactamase were examined. Double disc synergy test was used with Sftazydym 30Μ g, Ceftriaxone 30 μg, Aztreonam 30 μg, Cefotaxime 30 μg, Cefpodoxime 10 μg and amoxicillin clavulanate 30 μg discs to detect UTI E-coli. All data analyzed in SPSS version 19. Results: From 100 isolated E.coli, 69% and 31% of strains were isolated from women and men, respectively. The highest rate of infection were found in patients older than 60 years with abundancy 20% and 10% in men and in women, recpectively. In these patients the highest antibiotic resistance was observed by Cefotaxime (40%). ESBL-producing strains were found 48.1% and 26.08% in men and women, respectively. Conclusions: Due to the beta-lactam group of antibiotics are the most common drugs used in urinary tract infections, so data of resistance to these antibiotics is important. This can help in the treatment of patients.

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