Background & objectives: Urinary tract infections (UTIs) caused by extended-spectrum beta lactamase (ESBL)-producing bacteria have become a growing problem worldwide. The aim of this study was to investigate the prevalence of ESBL-producing bacteria in urine samples of hospitalized patients in Imam Khomeini hospital of Ardabil over a period of October 2011 to August 2012.

  Methods : A total of 400 urinary pathogens isolated from urine samples were included in the study. All isolates were identified by routine biochemical methods and antimicrobial susceptibility testing carried out by Kirby-Bauer method. Confirmatory test for production of ESBLs was performed by the combination disk tests. The results were interpreted according to the recommendation of CLSI.

  Results : Of 400 isolated bacteria, 267 were E.coli, 39 Klebsiella pneumoniae, 17 Klebsiella oxytoca, 16 Enterobacter cloacae, 15 Enterobacter aerogenese, 6 Enterobacter agglomerans, 8 Enterobacter sakazakji, 3 Citrobacter froundi, 2 Citrobacter diversus, 3 Proteus mirabilis, 4 Edvardsiella tarta, 3 Serratia marcesecens and 17 Morganella morganii all of which then were analyzed. ESBL was detected in 36.75% (147) of isolates. Eighty nine E.coli cases (77.4%), 15 Klebsiella pneumonia (13.04%), 2 Klebsiella oxytoca (1.74%), 3 Enterobacter aerogenese (2.6%), 4 Enterobacter cloacae (3.5%), 1 Citrobacter ferundi (0.86%), and 1 Morganella morganii (0.86%) were detected as ESBLs producers, respectively.

  Conclusion : Based on the results of this study, broad-spectrum beta-lactamase production in bacterial strains isolated from patients with urinary tract infection was very high and almost 40% of all bacterial species isolates were ESBLs producers. Because of the high prevalence of ESBL-producing bacteria in the urinary tract infections in hospitalized patients of our area, we would strongly suggest that the ESBL production should be considered in these patients.