Community- And Healthcare-Associated Methicillin-Resistant Staphylococcus Aureus Strains: An Investigation Into Household Transmission, Risk Factors, And Environmental Contamination

OBJECTIVE. To measure transmission frequencies and risk factors for household acquisition of community-associated and healthcare associated (HA-) methicillin-resistant Staphylococcus aureus (MRSA).DESIGN. Prospective cohort study from October 4, 2008, through December 3, 2012.SETTING. Seven acute care hospitals in or near Toronto, Canada.PARTICIPANTS. Total of 99 MRSA-colonized or MRSA-infected case patients and 183 household contacts.METHODS. Baseline interviews were conducted, and surveillance cultures were collected monthly for 3 months from household members, pets, and 8 prespecified high-use environmental locations. Isolates underwent pulsed-field gel electrophoresis and staphylococcal cassette chromosome mec typing.RESULTS. Overall, of 183 household contacts 89 (49%) were MRSA colonized, with 56 (31%) detected at baseline. MRSA transmission from index case to contacts negative at baseline occurred in 27 (40%) of 68 followed-up households. Strains were identical within households. The transmission risk for HA-MRSA was 39% compared with 40% (P=.95) for community-associated MRSA. HA-MRSA index cases were more likely to be older and not practice infection control measures (P=.002.03). Household acquisition risk factors included requiring assistance and sharing bath towels (P=.001.03). Environmental contamination was identified in 78 (79%) of 99 households and was more common in HA-MRSA households.CONCLUSION. Household transmission of community-associated and HA-MRSA strains was common and the difference in transmission risk was not statistically significant.