Household Environments Are a Key Reservoir for MRSA Transmission

Household environments serve as a key reservoir for the transmission of methicillin-resistant Staphylococcus aureus (MRSA), and common interventions such as frequent hand washing can help stop the spread. This is according to a new study that examined household surfaces, family members and pets for a detailed look at how the disease spreads.

The study, published in The Lancet Infectious Diseases, was conducted by investigators at the University of Chicago and Washington University School of Medicine who set out to better understand recurring infections and how MRSA affected multiple family members. The study team followed 692 individuals and 154 cats and dogs in 150 households that included children who had been treated for Staph infections between 2012 through 2015. Each home was visited 5 times within a 1-year period, with people, pets and household surfaces tested for MRSA.

“The level of detail engendered by this study is extremely unique,” corresponding author Stephanie A. Fritz, MD, MSCI, FAAP, FIDSA, FPIDS, associate professor of pediatrics at Washington University School of Medicine, told Contagion^®.

Investigators found S aureus on 513 (74%) of individuals, including MRSA on 319 (46%) of the individuals at least once during the study. Among pets, 68 (44%) had S aureus at least once, including 44 (29%) with MRSA. At least one household surface was contaminated with S aureus in 136 (91%) homes, including 104 (69%) with MRSA.

“Importantly, our longitudinal study revealed that household members acquiring a new strain of MRSA are at increased risk of developing a skin infection in the following months,” Fritz said. “Additionally, while we have traditionally thought of MRSA being spread through person-to-person contact, our study demonstrates that household environmental surfaces play a significant role in household MRSA transmission dynamics.”

In all, 3891 S aureus isolates were analyzed during the study, revealing their “bacterial fingerprint” and allowing investigators to distinguish between strains that were present in households and new strains introduced during the year of the study.

“We then amalgamated these fingerprints with very sophisticated statistical techniques to associate distinct hygiene and behavioral factors associated with modes of acquiring MRSA, specifically introductions and transmissions.” Fritz said.

Out of 703 acquisitions of S aureus among people sampled at least twice consecutively, 308 (44%) were introductions, 297 (42%) were transmissions and 98 (14%) were undetermined. Of the transmissions, environmental sites were a potential source in 178 and the sole source in 62.

The study found that straightforward interventions, such a frequent hand washing and not sharing towels and other personal hygiene items, are effective in disrupting the transmission and acquisition of the bacteria. Spread of MRSA was found to be more likely in homes with odor, clutter and grime, in rented and crowded homes, and when people share bedrooms, beds, towels and other hygiene items.

“Regarding the findings of the study, we asked EXTREMELY detailed questions regarding activities outside the household (e.g., occupation, attending a gym, hair and nail salons, public pools, etc) and specific hygiene behaviors (e.g., frequency of laundering each article of clothing and the water temperature used for laundering each item),” Fritz told Contagion^®. “We were surprised that rather straightforward or subtle activities, such as hand washing and sharing of personal hygiene items are most important, even when considering behaviors that one might theorize to be suspect, such as working in health care settings or playing contact sports or spending a lot of time at spas or nail/hair salons or gyms.”

An interesting finding is that pets were more likely to get MRSA from humans than to spread the bacteria to humans.

The investigators also gained insight into the personal experiences of the participants, including the stigma they faced due to MRSA diagnosis, which was the subject of a previous qualitative report.

“Previous community-based MRSA prevention studies have focused solely on MRSA eradication of people (through the use of topical antimicrobials and antiseptics),” Fritz told Contagion^®. “The findings of our study have informed the targets for intervention, and specifically, household environmental cleaning that may interrupt the transmission within these households. This trial is currently underway.”

In 2017, more than 119,000 bloodstream infections caused by S aureus led to the deaths of 20,000 people, according to the US Centers for Disease Control and Prevention, which noted that progress against the bacteria tapered off after 2013.

A study published earlier this year emphasized the importance of discharge education to help stop the spread of MRSA to home environments leading to post-hospital MRSA infections.