A new study (1) carried out in the US shows how the household environment plays a key role in transmission of community-associated MRSA. From this study the authors conclude that good hand hygiene was associated with a reduced spread of MRSA between an infected child and other family members and family pets.
This conclusion is in direct conflict with messages which appear in the media from time to time (2) telling us “we must stop washing our hands” as a means to “let” good bacteria into our body and build a healthy microbiome.
I suspect that the experts who have said this don’t actually mean “stop” washing hands, but that’s not the way it sounds to the public who read these media articles. This is the basis of a call to action in a policy paper entitled “Too clean or not too clean” released in 2018 by the Royal Society of Public Health (3) which said “Stakeholders with an interest in hygiene should work together to develop a common approach to hygiene in the home and everyday life, with consistent terminology, to avoid conflicting public messaging from different lobbying groups”
In this new study, healthy children with community-onset MRSA infections were recruited from a cohort study from hospitals and community practices in St Louis, USA. Household contacts (individuals sleeping in the home ≥four nights per week) and indoor dogs and cats were also enrolled. A baseline visit took place at the infected child’s primary home, followed by four quarterly visits over 12 months. At each visit, interviews were done and serial cultures were collected, to detect S aureus from three anatomic sites of household members, two anatomic sites on dogs and cats, and 21 environmental surfaces.
Across household members, pets, and environmental surfaces, 1267 MRSA acquisitions from household contacts or pets of the infected children were observed. MRSA acquisitions were driven equally by 510 introductions of novel strains into households and 602 transmissions within households, each associated with distinct factors. Frequent handwashing decreased the likelihood of novel strain introduction into the household. Transmission recipients were less likely to own their homes and were more likely to share bedrooms with strain colonised individuals, live in homes with higher environmental S aureus contamination burden, and report interval skin and soft tissue infection. Transmission sources were more likely to share bath towels whilst pets were often transmission recipients, but rarely the sole transmission source.
1. The full study can be found at Mork, R.L., Hogan, P.G., Muenks, C.E., Boyle, M.G., Thompson, R.M., Sullivan, M.L., Morelli, J.J., Seigel, J., Orscheln, R.C., Wardenburg, J.B. and Gehlert, S.J. 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. The Lancet Infectious Diseases. Published Online November 26, 2019. https://doi.org/10.1016/S1473-3099(19)30570-5
2. Examples of media articles can be found at:
• Now don’t wash your hands: why more dirt will make us more healthy http://www.thetimes.co.uk/tto/health/article4602687.ece
• Dog walkers and gardeners should avoid washing hands to encourage friendly bacteria http://www.telegraph.co.uk/news/health/news/12097838/Dog-walkers-and-gardeners-should-avoid-washing-hands-to-encourage-friendly-bacteria.html
• Don't wash your hands! A bit of dirt is good for you: Experts say cleaning less often would protect against allergies by allowing helpful bacteria into the body
• Fighting the germ of our near obsessive cleanliness http://www.mumbaimirror.com/others/health-lifestyle/Fighting-the-germ-of-our-near-obsessive-cleanliness/articleshow/50085504.cms?
3. Too clean or not too clean? The case for targeted hygiene in home and everyday life