en میکروب شناسی Microbiology مقالات اصلی Original Article <div style="text-align: justify;"><strong><em>Background:</em></strong> Among hospitalized patients, <em>Staphylococcus aureus</em> (<em>S. aureus</em>) infections pose a serious health threat. The present study investigated the frequency of biofilm forming genes among clinical isolates <em>S. aureus</em> and their susceptibility to antibiotics.<br> <br> <strong><em>Methods:</em></strong> The clinical samples were analyzed via standard biochemical assays for identifying different bacterium, which was then confirmed using the multiplex colony PCR method. Those samples identified as <em>S</em>. <em>aureus</em> were examined for the presence of the <em>cna, fnbA, fnbB</em> and <em>pvl</em> genes. The antibiotic susceptibility of the <em>S. aureus</em> isolates was then tested.<br> <br> <strong><em>Results:</em></strong> Using the standard biochemical assay approach, 54 <em>S. aureus </em>strains were identified. However, when using the multiplex PCR method 50 <em>S</em>. <em>aureus </em>strains were identified among the clinical samples. The <em>in vitro</em> biofilm formation assays determined 3 (6%) strains of <em>S. aureus</em> to be strong biofilm forming, 15 (30%) of the isolates were determined to be moderate biofilm forming and, 32 (64%) were determined to be weak biofilm forming. Among the isolated strains, the specific frequencies of the biofilm forming genes were determined to be 31 (62%) for <em>cna</em>, 35 (70%) for <em>fnbA</em>, 13 (26%) for <em>fnbB</em> and 1 (2%) for <em>pvl</em>. In 11 (22%) of the isolated strains <em>fnbA</em>, <em>fnbB</em> and cna genes were all present. All strains were determined to be penicillin, amoxicillin and clavulanic acid resistant. &nbsp;<br> <br> <strong><em>Conclusions:</em></strong> Due to the increase of the antibiotic resistance in biofilm producing S. <em>aureus</em> strains, rapid identification of antibiotic resistance can help to eliminate the infection effectively.</div> Biofilm, Multiplex colony PCR, Pertussis toxin, Spreading factors, Staphylococcus aureus. 181 188 http://rbmb.net/browse.php?a_code=A-10-137-1&slc_lang=en&sid=1 Mostafa Shahmoradi shahmoradimostafa7@gmail.com 100319475328460017069 100319475328460017069 No Department of Microbiology, Zanjan Branch, Islamic Azad University, Zanjan, Iran. Peyman Faridifar peyman.faridifar64@gmail.com 100319475328460017070 100319475328460017070 No Department of Microbiology, Zanjan Branch, Islamic Azad University, Zanjan, Iran. Reza Shapouri rezashapury@yahoo.com 100319475328460017071 100319475328460017071 No Department of Microbiology, Zanjan Branch, Islamic Azad University, Zanjan, Iran. Seyed Fazlollah Mousavi Mousavi@pastur.ac.ir 100319475328460017072 100319475328460017072 Yes Department of Microbiology, Microbial research center, Pasteur Institute of Iran, Tehran. Mahnaz Ezzedin Mhz.ezn@gmail.com 100319475328460017073 100319475328460017073 No Department of Microbiology, Islamic Azad University, Tehran branch, Tehran, Iran. Bahman Mirzaei b.mirzaei@mazums.ac.ir 100319475328460017074 100319475328460017074 No Department of Microbiology, Islamic Azad University, Tehran branch, Tehran, Iran. & Department of Medical Microbiology and Virology Faculty of Medicine, Mazandaran University of medical sciences, Sari, Iran.