en باکتری شناسی bacteriology Research Article Research Article <div style="text-align: justify;"><span style="font-size:12px;"><span style="font-family:Times New Roman;"><b>Background:</b> <i>Staphylococcus aureus</i> is one of the most common agents of nosocomial infection worldwide. Methicillin-resistant and biofilm-associated infections of this bacterium have become a clinical concern in patients. This research aimed to identify biofilm-forming ability and <i>accessory gene regulator</i> (<i>Agr</i>) - specific group of clinical isolates of methicillin-resistant <i>S. aureus</i> (MRSA) in Northern Iran.<br> <b>Methods:</b> In 2021, a total of 200 clinical isolates were identified as <i>S. aureus</i> by biochemical tests. The disk diffusion method was used to examine the antibiotic resistance of isolates and the microplate method was applied to investigate the biofilm production capability. In addition, the PCR method was used to determine the frequency of biofilm-associated genes and <i>Agr</i> typing of MRSA isolates. P &pound; 0.05 was considered significant.<br> <b>Results:</b> Overall, 62.5% of isolates were methicillin-resistant and 75% were multiple antibiotic-resistant. Biofilm-forming ability was detected in 99 (79.2%) methicillin-resistant isolates in which <i>ica</i>A and <i>ica</i>D were found in 85% and 78% of biofilm-producing isolates, respectively. Type 1 of the <i>Agr</i> gene was the most common type among methicillin-resistant isolates. The frequency of biofilm-associated genes showed a significant association with MDR phenotype and the presence of <i>Agr</i> locus (P &pound; 0.05).<br> <b>Conclusion</b>: The present findings indicate a high frequency of biofilm and antibacterial resistance in methicillin-resistant <i>S. aureus</i> isolates in Guilan Province. These findings suggest reliable and rapid identification of biofilm-forming MRSA strains to prevent the spread of these bacteria.</span></span><br> &nbsp;</div> Agr protein, Biofilms, Staphylococcus aureus, Methicillin resistance 24 26 http://mlj.goums.ac.ir/browse.php?a_code=A-10-1216-2&slc_lang=en&sid=1 Mahsa Aghaei m_aghaei@gmail.com 100319475328460028920 100319475328460028920 No Department of Biology, Rasht Branch, Islamic Azad University, Rasht, Iran Leila Asadpour l.asadpour@yahoo.com 100319475328460028921 100319475328460028921 Yes Department of Biology, Rasht Branch, Islamic Azad University, Rasht, Iran Amir Arasteh arasteh@iaurasht.ac.ir 100319475328460028922 100319475328460028922 No Department of Biology, Rasht Branch, Islamic Azad University, Rasht, Iran