en ميکروبيولوژي Microbiology پژوهشي Research <div style="text-align: justify;"><strong>Background: </strong>This study aimed to describe the association between age groups and antimicrobial susceptibility patterns, also integron presence in<em> Escherichia coli</em> and <em>Klebsiella pneumoniae</em> isolates from Tabriz, Iran.<br> <strong>Methods:</strong> 140 isolates of <em>E. coli </em>and 150 isolates of <em>K. pneumoniae</em>, both comprising the same number of children and adult isolates were examined for susceptibility to 13 routine antibiotics. The integron existence in multidrug resistant (MDR) isolates was also determined using PCR-RFLP.<br> <strong>Results: </strong>The significant age related differences were observed in the resistant rates of <em>K. pneumonia</em>e toward cotrimoxazol, nalidixic acid, ciprofloxacin and norfloxacin. For <em>E. coli,</em> age related differences in the resistance rates to tetracycline, chloramphenicol, ciprofloxacin and norfloxacin were significant. PCR-RFLP results revealed the presence of class 1 integron (<em>intI</em>1) in 24.5% and 19.2% of MDR <em>E. coli</em> in children and adults, respectively. In <em>K. pneumonia</em>e, 72.9% of children and 84% of adults isolates were positive for <em>intI</em>1. The prevalence of class 2 integrons was significantly associated with age group, in both <em>E. coli</em> and <em>K. pneumoniae.</em> No class 3 integrons were detected in this study.<br> <strong>Conclusions:</strong> The resistance rates differ across age groups. Moreover, this study is the first that demonstrated age related differences in the integron &nbsp;presence, especially class 2 integrons, in <em>E. coli</em> and<em> K. pneumoniae</em>.</div> Integron, E. coli, K. pneumoniae, Children, Adult 30 40 http://rmm.mazums.ac.ir/browse.php?a_code=A-10-907-1&slc_lang=en&sid=1 Vajihe Sheikhalizadeh vajihesheikhalizade@yahoo.com 10031947532846007219 10031947532846007219 Yes Department of Medical Microbiology, Faculty of Medicine, Tabriz University of Medical Sciences, Tabriz, Iran Mohammad Ahangarzadeh Rezaee rezaee@tbzmed.ac.ir 10031947532846007220 10031947532846007220 No Immunology Research Center and Department of Medical Microbiology Faculty of Medicine, Tabriz University of Medical Sciences, Tabriz, Iran Nastaran Langarizadeh nas.langarizadeh@gmail.com 10031947532846007221 10031947532846007221 No Department of Biotechnology, Ege University, Izmir, Turkey Hamid Reza Goli 10031947532846007222 10031947532846007222 No Department of Microbiology, Faculty of Medicine, Mazandaran university of medical sciences