Background: Escherichia coli is the most causative agent of urinary tract infections [UTIs] . Apart from all human infectious diseases, UTI have a high prevalence and in most cases, Escherichia coli is a dominance bacterium which can cause pyelonephritis and cystitis. The aim of the study was to determine the occurrence of some virulence genes expressing fimbriae, production of hemolysin and aerobactin among a hundred Escherichia coli isolates obtained from in-and outpatients of Karaj Shahid Rajaii hospital, showing clinical and laboratory signs of UTI. Materials and Methods: In this investigation we isolated Escherichia coli strains from urine samples of patients with UTI during the period of July to December 2012 and studied them for the presence of the virulence genes by PCR.
Results and Conclusion: The most abundant virulence factor in this study was fimH. The prevalence of the virulence factors for fimbriae type 1 [fimH gene] , pyelonephritis associated pili [pap gene] , S-family adhesions [sfa gene] , hemolysin [hly gene] and aerobactin [aer gene] , was 73%, 46%, 32%, 47%, 57%, respectively.