en Microbiology پژوهشي Research <strong>Introduction:</strong> AmpC &beta;-lactamases are among the most important cephalosporinases. Production of AmpC &beta;-lactamase in microorganisms is often associated with multidrug resistance and limited treatment options. This study aimed to determine antimicrobial susceptibility pattern and frequency of AmpC &beta;-lactamase genes in <em>Escherichia coli</em> strains isolated from urinary tract infections. <strong>Materials and Methods:</strong> The study included 154 <em>E. coli</em> isolates from urine samples of patients in medical centers of Gorgan, Iran. Cefoxitin-resistance was evaluated by the Kirby-Bauer method.&nbsp; Cefoxitin-resistant strains were evaluated using cefoxitin disks alone and combined with boronic acid to confirm presence of AmpC &beta;-lactamase. Presence of <em>MOX</em> gene was investigated by polymerase chain reaction. <strong>Results:</strong> Among the 154 <em>E. coli</em> isolates, 37 (24%) were cefoxitin-resistant, 16 of which were found to be AmpC &beta;-lactamase-positive in the phenotypic test. In addition, the MOX gene was found in two isolates. <strong>Conclusions:</strong> The frequency of AmpC &beta;-lactamase-producing E. coli and MOX gene in Gorgan is close to the regional and national average.&nbsp; Escherichia coli, urinary tract infection, AmpC β-lactamase 1 8 http://jcbr.goums.ac.ir/browse.php?a_code=A-10-60-4&slc_lang=en&sid=1 Mahdi Arab Zoozani مهدی عرب زوزنی 10031947532846001672 10031947532846001672 No Department of Microbiology, Faculty of Medical Sciences, Golestan University of Medical Sciences, Gorgan, Iran Ezzat Allah Ghaemi عزت اله قائمی 10031947532846001673 10031947532846001673 No Department of Microbiology, Faculty of Medical Sciences, Golestan University of Medical Sciences, Gorgan, Iran Ailar Jamalli آیلر جمالی 10031947532846001674 10031947532846001674 Yes Laboratory Sciences Research Center, Golestan University of Medical Sciences, Gorgan, Iran