Background and Objective: Escherichia coli strains are the major cause of urinary tract infections which belong to the large group of extra-intestinal pathogenic E. coli. They fall into four main phylogenetic groups: A, B1, B2 and D. The aim of the present study was to determine phylogenetic groups in uropathogenic and commensal Escherichia coli isolated. Also, due to increase in the rate of antibiotic usage and subsequent drug resistance, this study evaluated the antimicrobial resistance pattern of E. coli isolated from patients with UTI.

Materials and Methods: In this cross-sectional study, 137 uropathogenic Escherichia coli isolates were collected from the clinical specimens of Zanjan hospitals and 50 isolates were collected from healthy adults. After verifying isolates via biochemical methods and extraction of total DNA, Multiplex PCR was done by specific primers for phylogenetic grouping. The antibiotic susceptibility test (disk diffusion method) was done according to CLSI advice against 13 antibiotics.

Results: In this study, the highest rates of resistance to antibiotics in UTI isolates were seen against ampicillin (74.5%) and aztreonam (59.1%). Also, the lowest rates of resistance were reported against imipenem (1.5%) and amikacin (10.9%).The distribution of UPEC phy logenetic groups typing marked the highest prevalence in group B2 (67.15 %) , and then in group D (21.17%) and the lowest prevalence in group A (11.68%). Phy logenetic B1 was not observed in uropathogenic isolates. Among the commensal isolates, 52% belonged to phylogenetic group D, 24% to B2, 14% to A, and10% to B1.

Conclusion: The results indicate the higher prevalence of B2 and D phylogenetic groups in commensal and uropathogenic Escherichia coli strains in Zanjan.