Iranian CA-MRSA strains are genetically diverse with an elevated prevalence of t790/ST22 SCCmec IV isolates. These findings support the need for more effective infection control measures to reduce nasal carriage and prevent dissemination of CA-MRSA in Iran.

Background:Nasal carriage of Staphylococcus aureus plays an important role in the pathogenesis of staphylococcal infections. Anterior nasal region is a primary origin of S. aureus. In longitudinal studies, three types of S. aureus nasal carriers can be distinguished: persistent carriers, intermittent or transient carriers, and noncarriers.Objectives:This study was designed to determine the dynamic of S. aureus nasal carriage in healthy carriers of central Iran.Patients and Methods:A total of 813 healthy adults were subjected to this cross-sectional study from November 2011 to January 2012 in Arak University of Medical Sciences. Two anterior nasal swabs were taken with a week interval from each participant. All the isolates were identified as S. aureus phenotypically by standard laboratory methods. The isolates were reconfirmed by amplification of sa442 gene as the identification marker. All the isolates were screened for the presence of the PVL (Panton-Valentine leukocidin) virulence genes and arginine catabolic mobile element (ACME-arc).Results:Among the 813 subjects screened, 83 (10.2%) were persistent carriers, 86 (10.6%) were transient carriers and 644 (79.2%) cases were found as noncarriers. A total of 169 (20.8%) participants had colonized S. aureus. The frequency of ACME–arc A and PVL genes in S. aureus strains were 17% and 20%, respectively.Conclusions:Carriage of PVL-positive S. aureus is common in this region, even in the low frequency of MRSA colonization. The detection of ACME-arcA gene in S. aureus isolates is a public-health concern and demands continued surveillance and close monitoring.