The Burden of MRSA and S aureus in Nursing Homes


How many nursing homes have these microbes?

Environmental contamination is a prime source of disease transmission in a health care environment. In fact, the cleaning and disinfection of high-touch surfaces and medical equipment is a critical component of infection prevention efforts. While we focus heavily on acute care hospitals as hubs for disease transmission and the need for infection prevention efforts, it’s important that we remember an all too neglected care environment—the nursing home.

The US Centers for Disease Control and Prevention (CDC) reports that in the United States, there are roughly 15,600 nursing homes with 1.7 million licensed beds. Furthermore, they note that in 2015, there were 1.3 million residents of nursing homes. These findings point to a considerable population of patients in a health care environment that requires little infection prevention oversight.

In the quest to understand the true microbial burden and risk for infectious diseases in nursing homes, investigators from Kent State University in Ohio, studied the prevalence of Staphylococcus aureus and methicillin-resistant Staphylococcus aureus (MRSA) in Ohio nursing homes. Their findings were published in the American Journal of Infection Control.

Seven nursing homes were studied in the Northeast Ohio area, each with 75-120 beds. The group represented rural and urban, and the focus on the 2 specific organisms was related to both the wide range of infections they can cause, but also the high rate of colonization within the United States.

Environmental samples were collected with the input from staff and general workflow. Overall, the research team collected samples from 37 surfaces, which was standardized across all the nursing homes. Of the 259 environmental swabs collected across the 7 nursing homes, they found an overall prevalence of S aureus was 28.6% and the prevalence of MRSA and MSSA (methicillin-sensitive S aureus) being 20.1%.

Interestingly, the overall prevalence of S aureus in suburban, urban, and rural sites was 25.7%, but no MRSA was found in rural sites. MRSA was found in suburban and urban nursing homes, with an overall prevalence of 16.9%. An interesting finding was that those nursing homes in urban areas, had a statistically significant higher rate of S aureus compared to those in non-urban areas (45.9% versus 21.6%).

Of those areas sampled, the most common isolates that yielded microbial contamination were those that nurses touched more frequently, including chart folders, keyboards at nursing stations, and nursing car countertops. These high-touch areas were observed for roughly 60% of the nursing homes. Wheelchair arms were also a considerable source for contamination, with 42.9% yielding positive microbial findings.

Investigators also tested the S aureus isolates for antibiotic susceptibility. All of those isolates were resistant to benzylpenicillin, 70.3% were resistant to oxacillin, and 8.1% were resistant to gentamicin. Interestingly, roughly 65% were resistant to levofloxacin and erythromycin. Those samples collected from urban and suburban nursing homes yielded the highest percentages of multidrug-resistant isolates.

The investigators ultimately note that while it is well known that colonization with MRSA in nursing homes is a common occurrence, the transmission dynamics are still poorly known. The differences in S aureus and MRSA prevalence in different regions are likely linked to the patient transfers they receive from nearby hospitals (urban nursing homes had 4-15 hospitals nearby, while those suburban and rural nursing homes had 1-3 nearby hospitals).

Further consideration should be given to the role of hospitals in the transmission chain for nursing home patients. Lastly, it is important that more attention and support be given to disinfection and cleaning in these environments and other infection prevention measures.

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