Causative agents and antimicrobial susceptibilities of urinary tract infections in the northwest of Iran

Background: The empirical therapy of urinary tract infections (UTI) relies on the predictability of the agents causing UTI and knowledge of their antimicrobial susceptibility patterns. Methods: In a prospective study undertaken over a 14-month period, 5136 samples from patients suspected of having a UTI were analyzed, of which 676 were culture-positive. Isolated bacteria were identified by standard tests, and antibiotic susceptibility was determined by disk diffusion method. Results: According to our results, Escherichia coli was the most common etiological agent of UTI (74.6%), followed by Klebsiella spp(11.7%), Staphylococcus saprophyticus(6.4%), and Pseudomonas aeruginosa(2.2%). Analysis of the frequency of isolated bacteria according to the age of the patients revealed that Klebsiella infections are more prevalent in the older age groups (>10 years) and Pseudomonas infections are more prevalent in children and the elderly (<9 years and >60 years). Results of antimicrobial susceptibility analysis for E. coli, as the most prevalent cause of UTI, to commonly used antibiotics are as follows: amikacin (97.8%), gentamicin (97%), ciprofloxacin (94%), nitrofurantoin (87.1%), nalidixic acid (93.7%), trimethoprim-sulfamethoxazole (48.2%), cephalexin (76%), and ampicillin (6.9%). Conclusions: The results show that the antimicrobial resistance patterns of the causes of UTI are highly variable and continuous surveillance of trends in resistance patterns of uropathogens is important. (C) 2008 International Society for Infectious Diseases. Published by Elsevier Ltd. All rights reserved.