Household Transmission of MRSA Skin and Soft Tissue Infections

According to data published in The Lancet Infectious Diseases, the household environment plays a key role in the transmission of community-associated methicillin-resistant Staphylococcus aureus (MRSA) skin and soft tissue infections.

An understanding of the factors underlying MRSA acquisition are essential for effective, targeted prevention strategies. To investigate household transmission dynamics investigators recruited otherwise healthy pediatric patients with culture-confirmed, community-onset MRSA infections from 2012 to 2015. Household contacts including individuals sleeping in the home ≥4 nights per week and indoor dogs and cats were also enrolled. A baseline visit, followed by quarterly visits over a 12-month period were conducted during which interviews were done and serial cultures collected.

The results found 1267 strain acquisition events across household members, pets, and environmental surfaces.  Acquisitions were driven equally by introductions of novel strains and transmissions within households (510 and 602 transmissions, respectively), each with distinct associated factors.

The likelihood of novel strain introduction was decreased by frequent handwashing (odds ratio [OR], 0.86; 95% credible interval [CrI], 0.74–1.01). Transmission recipients were less likely to own their own home (OR, 0.77; 95% CrI, 0.63-0.94) and more likely to share bedrooms with strain-colonised individuals (OR, 1.33; 95% CrI, 1.12-1.58), live in homes with higher environmental S aureus contamination burden (OR, 3.97; 95% CrI, 1.96-8.20) and report interval skin and soft tissue infection (OR 1.32; 95% CrI, 1.07-1.64). Transmission sources were also more likely to share bath towels (OR, 1.25; 95% CrI, 1.01-1.57). While pets were often transmission recipients, they were rarely the source.

Investigators reported several study limitations. Definitive association of incident skin and soft tissue infections with individual acquisition events was not possible due to unavailability of isolates from interval skin and soft tissue infections. The results may not be generalizable to geographic locales with lower prevalence of MRSA colonization and incidence of skin and soft tissue infection. Furthermore, results may also not be generalizable to adult-only households as all index patients were children.

Investigators concluded that MRSA is acquired via introductions from outside sources and within-household transmissions. Both of these routes were found to exhibit distinct hygiene and behavioral characteristics. Investigators recommended that straightforward changes in household practices such as handwashing and sharing practices could mitigate introductions and transmission. They further suggested that prospective studies of high-risk populations should test targeted decolonization regimens for sources, as well as protective hygiene practices for their cognate recipients, combined with targeted decontamination of environmental surfaces.

Reference

Mork RL, Hogan PG, Muenks CE, et al. Longitudinal, strain-specific Staphylococcus aureus introduction and transmission events in households of children with community-associated meticillin-resistant S aureus skin and soft tissue infection: a prospective cohort study [published online November 26 2019]. Lancet Infect Dis. doi:10.1016/S1473-3099(19)30570-5