Risk factors for and molecular characteristics of methicillin-resistant Staphylococcus aureus nasal colonization among healthy children in southern Taiwan, 2005–2010

Background/purpose: Nasal colonization of Staphylococcus aureus is a well-defined risk factor for subsequent infection. This study investigated the prevalence of methicillin-resistant S. aureus (MRSA) in southern Taiwan and aimed to identify the host factors for S. aureus colonization and the virulence factor of Panton-Valentine Leukocidin (PVL) genes. Methods: In a hospital-based study in Kaohsiung from Oct. 2005 to Dec. 2010, we performed nasal swab in the healthy children aged 2–60 months. We examined the relationship between the demographic characteristics and S. aureus nasal colonization. MRSA isolates were further analyzed for antimicrobial susceptibility and molecular characteristics. Results: Among 3020 healthy children, 840 (27.8%) children had S. aureus nasal colonization. Of 840 isolates, 246 (29.3%) isolates were MRSA. MRSA colonization was significantly associated with age 2–6 months, day care attendance, and influenza vaccination. Breastfeeding was a protective factor against MRSA colonization. Most MRSA isolates were susceptible to trimethoprim-sulfamethoxazole and doxycycline. Ninety-four percent of MRSA isolates carried either type IV staphylococcal cassette chromosome mec (SCCmec) or SCCmec V_T and 87% belonged to the local community strains, namely clonal complex 59/SCCmec IV or V_T. MRSA isolates with PVL-negative was associated with children with passive smoking. Conclusions: Between 2005 and 2010, 27.8% and 8.14% of healthy children in southern Taiwan had nasal carriage of S. aureus and MRSA, respectively. Most MRSA isolates were local community strains. Several demographic factors associated with nasal MRSA colonization were identified.