en Epidemiologic studies including microbial genotyping, phenotyping and serotyping Epidemiologic studies including microbial genotyping, phenotyping and serotyping Original article Original article <p><a name="OLE_LINK62"></a><a name="OLE_LINK58"><strong>Introduction:</strong> Methicillin-Resistant <em>Staphylococcus aureus</em> (MRSA) is responsible for an increasing number of serious hospital- and community-acquired infections. USA300 is known to be the most common cause of community-acquired infections, but recently there have been some reports on hospital-acquired infections caused by this strain. <strong>Methods</strong><strong><span dir="RTL">:</span></strong> Totally 171 isolates of <em>S. aureus</em> were collected from different clinical samples in selected university hospitals in Mashhad, Tehran, and Isfahan cities. Then, they were assessed by agar screening and disk diffusion methods to determine their resistance to Methicillin. The isolated MRSA strains were confirmed by detection of <em>mecA</em> gene. The staphylococcal cassette chromosome <em>mec</em> (SCC<em>mec</em>),<em> agr</em>, and <em>spa</em> typing and also detection of Panton-Valentine leukocidin (<em>PVL</em>) and arginine catabolic mobile element (<em>ACME</em>) genes were performed on <em>mecA</em> harboring isolates. Multilocus sequence typing was performed on <em>PVL</em>/<em>ACME</em> positive MRSA strains. <strong>Results:</strong> We found a <em>PVL/ACME</em> positive MRSA isolate. Genetic evaluation results for this isolate produced the following profile: positive for <em>mecA</em>, <em>pvl</em>, <em>arcA</em>, and <em>hla </em>genes, negative for <em>vanA, sec</em>, and <em>tst1</em>, and belonged to<em> agr </em>I, SCC<em>mec </em>IV, sequence type 8 (ST8), and<em> spa </em>t008. <strong>Conclusion:</strong> Our results suggest a finding of USA300CA-MRSA isolate in Mashhad, Iran. This is an uncommon finding, because USA300 is routinely found in areas other than Middle East. A notable point about these isolates is that they belong to American</a> Endemic clones.</p> Staphylococcus aureus, Methicillin-Resistant, Panton-Valentine leukocidin, Iran. 100 104 http://jommid.pasteur.ac.ir/browse.php?a_code=A-10-62-1&slc_lang=en&sid=1 Amir Azimian amir_azimian2003@yahoo.com No Department of Pathobiology and Laboratory Science, School of Medicine, North Khorasan University of Medical Sciences, Bojnurd, Iran. Seyed Asghar Havaei havaei.seyedasghar@gmail.com Yes Department of Microbiology, School of Medicine, Isfahan University of Medical Sciences, Isfahan, Iran. kiarsh Ghazvini kiarash_ghazvini@yahoo.com No Department of microbiology, School of Medicine, Mashhad University of Medical Sciences, Mashhad, Iran. Mahsa Khosrojerdi khosrojerdi_mahsa@yahoo.com No Department of Pediatrics, School of Medicine, Semnan University of Medical Sciences, Semnan, Iran. Mahmood Naderi mahmood.naderi@gmail.com No Molecular Biology and Genetic Engineering Department, Stem Cell Technology Research Center, Tehran, Iran. Siamak Samiee siamak_samiee@yahoo.com No Reference Health Laboratories, Ministry of Health and Medical Education, Tehran, Iran.