en Anti-microbial agents, resistance and treatment protocols Anti-microbial agents, resistance and treatment protocols Original article Original article <div style="text-align: justify;"><strong>Introduction: </strong>This study aimed to determine the frequency of extended-spectrum beta-lactamases (ESBL) and different drug resistance phenotypes in <em>Enterobacteriaceae</em> isolated from clinical specimens in Gonbad-e Kavus, Golestan Province. <strong>Methods:</strong> 220 clinical samples of urine, blood, pus, sputum, CSF, body fluids, and ear and eye discharge were collected during six months from April to September 2021 at a referral hospital. The samples were cultured on blood and MacConkey agar and incubated overnight at 37 &deg;C. Standard biochemical tests and the API20E enteric identification system were used to identify bacteria. The Kirby-Bauer disk diffusion method determined the antibiotic resistance pattern, and the phenotypic confirmatory test was used for detecting ESBL producers. <strong>Results: </strong>108 <em>Enterobacteriaceae</em> isolates were identified from different clinical specimens out of the samples. The isolates were <em>Escherichia coli</em> (36.1%), <em>Klebsiella pneumonia</em> (25%), <em>Enterobacter</em> <em>cloacae</em> (18.5%), <em>Citrobacter</em> <em>freundii</em> (11.1%) and <em>Proteus mirabilis</em> (9.2%). The highest resistance and susceptibility among the isolates belonged to sulfamethoxazole-trimethoprim (68.5%) and meropenem (11.1%), respectively. The highest prevalence of multidrug-resistant (MDR) and ESBL were observed in<em> E. coli</em> and<em> Proteus mirabilis </em>isolates<em>.</em> <strong>Conclusions:</strong> In this study, the high frequency of MDR phenotypes in the isolates may suggest an increasing trend of antibiotic resistance in<em> Enterobacteriaceae</em>. This could greatly impact the management and treatment of infections caused by these drug-resistant bacteria. Therefore, infection-control measures and continuous monitoring is recommended for controlling the spread of ESBL-producing strains in different geographical areas.</div> Beta-lactamases, Drug-resistant, Enterobacteriaceae, Prevalence 19 23 http://jommid.pasteur.ac.ir/browse.php?a_code=A-10-310-3&slc_lang=en&sid=1 Mohammad Hossein Akbari Hosseinakbari172@gmail.com 0000-0003-2807-0580 No Department of Microbiology, Gorgan Branch, Islamic Azad University, Gorgan, Iran. Ania Ahani Azari ania_783@yahoo.com 0000-0001-7025-6739 Yes Department of Microbiology, Gorgan Branch, Islamic Azad University, Gorgan, Iran. Leila Fozouni lili_kia@yahoo.com 0000-0002-2248-0354 No Department of Microbiology, Gorgan Branch, Islamic Azad University, Gorgan, Iran.