en ميکروب شناسي Microbiology Research Article Research Article <div style="text-align: justify;"><span style="font-family:Times New Roman;"><span style="font-size:12px;"><b>Background:</b> Infections caused by extended-spectrum &beta;-lactamase (ESBL)-producing <i>Pseudomonas aeruginosa</i> (<i>P. aeruginosa</i>) are a serious concern in hospitals around the world. Many &beta;-lactamase genes are carried by integrons. This study was conducted to investigate the frequency of &beta;-lactamase genes and characterize class 1 integrons in multidrug-resistant <i>P. aeruginosa</i> strains in Guilan, northern Iran.<br> <b>Methods:</b> A total of 110 <i>P. aeruginosa</i> isolates were collected from different hospitals in 2021 and identified using standard microbiological methods. The isolates were studied for their antibacterial susceptibility and ESBL-producing ability by disk diffusion. All ESBL-producing isolates were investigated for the presence of &beta;-lactamase resistance and integron genes by polymerase chain reaction (PCR). Gene cassette screening was done based on sequence analysis of class 1 integrons.<br> <b>Results:</b> Based on antibiotic susceptibility testing, 40 isolates (37.4%) were ESBL producers. The frequency of &beta;-lactamase genes, including <i>VIM, SIM, IMP, SPM</i>, and <i>OXA2</i>, was 10.3%, 1.9%, 20.6%, 14%, and 4%, respectively. <i>GIM</i> and <i>OXA</i> 10 genes were not found in any of the strains. Furthermore, the <i>int1</i> gene was identified among 37 isolates (34.6%). The sequencing results of <i>int1</i> showed 12 different types of gene cassettes among 13 strains. In this assay, <i>blaOXA-2</i> was the only bla gene identified in <i>int1</i>.<br> <b>Conclusion</b>: The integrons carrying multidrug resistance genes are highly prevalent in <i>P. aeruginosa</i> isolates, and ESBL genes were also observed in these strains. Therefore, constant monitoring of drug resistance, especially ESBL producers, is critical to disease management in clinical settings.</span></span><br> &nbsp;</div> Pseudomonas aeruginosa, Integrons, β-lactamase genes, Gene cassette 27 31 http://mlj.goums.ac.ir/browse.php?a_code=A-10-1216-3&slc_lang=en&sid=1 Tahereh Panahi panahi.t22@yahoo.com 100319475328460029874 0009-0001-5893-9179 No Department of Biology, Rasht Branch, Islamic Azad University, Rasht, Iran Leila Asadpour l.asadpour@yahoo.com 100319475328460029875 100319475328460029875 Yes Department of Biology, Rasht Branch, Islamic Azad University, Rasht, Iran Najmeh Ranji najmeh.ranji@gmail.com 100319475328460029876 100319475328460029876 No Department of Biology, Rasht Branch, Islamic Azad University, Rasht, Iran