en Medical Bacteriology Medical Bacteriology Original Research Original Research <strong>Background: </strong>Uropathogenic Klebsiella pneumoniae is one of the well-kown uropathogens that have the main rule in biofilm formation. Increased prevalence of ESBL enzyme is one of the therapeutic problems. However, the aims of this study were to characterize&nbsp; the ability of biofilm formation and ESBL-producing isolates produced by urinary tract infection&rsquo;s K. pneumoniae to identify the prevalence of this type of infection in the studied area.<br> &nbsp;&nbsp; <strong>Methods:</strong> Between the 500 nonrepetitive clinical isolates, 128 isolates were detected as K. pneumoniae. Biofilm production of these isolates was showed by Merrit and Christensen method. The standard Kirby-Bauer disk diffusion method was used for antimicrobial susceptibility testing.&nbsp; The phenotype ESBL was confirmed by double disc synergy test (DDST). Genotypic identification of ESBLs did by molecular detection. The statistical analysis was done&nbsp; using software IBM SPSS Statistics (SPSS Inc) and chi-square and Fisher exact tests.<br> <strong>&nbsp;&nbsp; Results:</strong> The result of microtiter plate was observed and it was found that 86 (67.2%) isolates had weak biofilm, 24 (18.8%)&nbsp; moderate biofilm, and 18 (14.1%) strong biofilm. Also, 57 (44.5%) out of 128 isolates were diagnosed as MDR. The highest frequency of resistance was identified for cefotaxime 60 (46.9%) and tetracycline 60 (46.9%), and the lowest rate was for amikacin 16 (12.5%). The results of DDST showed 55 of 128 (43%) produced ESBL enzymes. PCR detection in ESBL-producing isolates showed contained bla_TEM &nbsp;33 of 55(63.1%), and bla_VEB &nbsp;13 of 55 (23% ). Also, 1 of 55 (2%) had both bla_TEM and bla_VEB. Also, 5 of 13 (38.4%) isolates that had the bla_VEB gene were also MDR and had weak biofilm (8/13; 61.5%),&nbsp; intermediate biofilm (3/13; 23%),&nbsp; and strong biofilm (2/13; 15.4%).<br> &nbsp;&nbsp; <strong>Conclusion:</strong> To decrease treatment complications and mortality rate of drug-resistant bacterial infections, rapid detection of &beta;-lactamases genes and evaluation of these properties and infection management programs can help to prevent the transmission of drug resistant-strains.<br> &nbsp; Extended-spectrum β-lactamases (ESBLs), Biofilm Formation, Klebsiella pneumonia, Antibiotic resistance, blaTEM, blaVEB 563 567 http://mjiri.iums.ac.ir/browse.php?a_code=A-10-6089-1&slc_lang=en&sid=1 Elham Haghighifar el.haghighifar@gmail.com 200319475328460063176 200319475328460063176 No Department of Microbiology, School of Medicine, Isfahan University of Medical Sciences, Isfahan, Iran Fatemeh Norouzi Fn.microbiology@yahoo.com 200319475328460063177 200319475328460063177 No Department of Microbiology, School of Medicine, Fasa University of Medical Sciences, Fasa, Iran Razie Kamali Dolatabadi r.kamali@resident.mui.ac.ir 200319475328460063178 200319475328460063178 Yes Department of Microbiology, School of Medicine, Isfahan University of Medical Sciences, Isfahan, Iran