47 Methicillin-Resistant Staphylococcus Aureus (MRSA) in Healthy Children: Risk Factor (RF) Analysis and Pulsed Field Gel Electrophoresis (PFGE) of Colonizing and Invasive Strains.

Abstract

Background: Staphylococcus aureus (SA) disease is common in colonized persons. The number of patients with MRSA colonization/infection increased from 443 to 736 in our institution from 2004 to 2005. MRSA infection has become a common consultation. Recent national studies have documented SA carriage 26-36% and MRSA 0.8-9%. Methods: We prospectively studied nasal MRSA carriage from 5/05-3/06 in children at an urban clinic (Site A: mainly Medicaid) or urgent care (Site B: mainly private payer). We reviewed RFs (daycare, prior antibiotic, hospitalization, skin disorders, needle use/tatoo, chronic illness, team sport participation, and healthcare exposure) of patients and their household contacts. Both anterior nares were swabbed and transport media was used. Swabs were plated on standard media. SA was identified by Staphaurex latex test. Susceptibilities were performed by automated micro-broth dilution. Invasive MRSA isolates were collected for 6 months and RFs were documented from chart. All MRSA strains were typed by PFGE. Results: Nasal swabs were obtained from 377 children; 44% girls; median age 4.9 years (3m-12y). Overall, SA was identified in 98 (26%), 10 (2.7%) were MRSA; colonization rates peaked in August. Site A patients had a lower rate of SA colonization, but a higher rate of MRSA. Compared to methicillin susceptible SA, MRSA were more often clindamycin susceptible and erythromycin resistant. No single RF statistically predicted MRSA carriage from children or their contacts. RF analysis between the invasive MRSA group (n=31) and the colonized group did not show a statistical difference. PFGE typing confirmed invasive and colonizing strains to be USA 100 or 300 without predominance. Conclusion: MRSA nasal carriage rates were lower than expected, especially given increasing clinical MRSA disease. Risk stratification did not predict MRSA carriage or invasive disease, but N was small. PFGE types were consistent with national data.