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Risk Factors for Household Transmission of Community-associated Methicillin-resistant Staphylococcus aureus

Nerby, Jessica M. MPH, CLS*; Gorwitz, Rachel MD, MPH; Lesher, Lindsey MPH*; Juni, Billie MS; Jawahir, Selina BS; Lynfield, Ruth MD*; Harriman, Kathleen PhD, MPH*

The Pediatric Infectious Disease Journal: November 2011 - Volume 30 - Issue 11 - p 927-932
doi: 10.1097/INF.0b013e31822256c3
Original Studies

Background: Methicillin-resistant Staphylococcus aureus (MRSA) has emerged as a community pathogen. Community-associated (CA) MRSA infections have occurred among multiple members of a household. We describe the incidence of and risk factors for MRSA colonization among household contacts of children with CA-MRSA infections.

Methods: MRSA-infected children <18 years of age who lacked established healthcare-associated MRSA risk factors were identified through surveillance at 12 Minnesota hospital laboratories. Nasal swab specimens and information on medical history and hygiene behaviors were collected from case-patients and enrolled household contacts during home visits. S. aureus isolates obtained from nasal cultures were screened for oxacillin resistance.

Results: In all, 236 households consisting of 236 case-patients and 712 household contacts were enrolled. Home visits were conducted on an average of 69 days after the onset of symptom in case-patients (range: 16–178 days). Twenty-nine (13%) case-patients and 82 (12%) household contacts had MRSA nasal colonization. Nasal MRSA colonization in ≥1 household contact occurred in 58 (25%) households. Household contacts who assisted the case-patient to bathe or who shared balms/ointments/lotion with the case-patient were more likely to be colonized (P < 0.01, P < 0.05), whereas those who reported using antibacterial versus nonantibacterial soap for hand washing were less likely to be colonized (P < 0.05) with MRSA clonally related to the case-patient infection isolate.

Conclusions: Only 13% of case-patients had MRSA nasal colonization on an average of 69 days after their initial MRSA infection. CA-MRSA colonization may be short-lived or may occur at non-nasal sites. One quarter of households had at least one household contact colonized with MRSA. Modifiable behaviors, such as sharing personal items, may contribute to transmission.

From the *Minnesota Department of Health, St. Paul, MN; †Centers for Disease Control and Prevention, Atlanta, GA; and ‡Minnesota Department of Health, Public Health Laboratories, St. Paul, MN.

Accepted for publication May 1, 2011.

Supported by a cooperative grant from the Centers for Disease Control and Prevention (Grant U01 C1000289–01).

The authors have no other funding or conflicts of interest to disclose.

The findings and conclusions in this report are those of the authors, and do not necessarily represent the official position of the Centers for Disease Control and Prevention.

Address for correspondence: Jessica M. Nerby, MPH, CLS, Minnesota Department of Health, Infectious Disease Epidemiology Prevention and Control Section, 625 N Robert St., PO Box 64975, Saint Paul, MN 55164. E-mail:

© 2011 by Lippincott Williams & Wilkins, Inc.