To the best of our knowledge, this is one of the first studies of MRSA environmental contamination in nursing homes that examined associations between MRSA contamination, cleaning quality, and infection control practices. We found that environmental contamination with MRSA was common, especially in nursing homes that had a large difference between point prevalence compared to what is imported from admitted patients (admission prevalence). Our findings suggest that environmental contamination with MRSA may contribute to the burden of MRSA in nursing homes.
Nursing homes face unique infection control challenges. Due to the importance of maintaining a home-like environment, residents in nursing homes often freely interact in common areas regardless of MRSA status. In turn, the common spaces where residents mingle, including dining rooms, recreation rooms, and rehabilitation rooms, may be much more relevant to infection control and prevention efforts than in the traditional hospital setting. Improving environmental cleaning in nursing homes may be a practical alternative to more restrictive methods, such as contact isolation policies, used in hospitals.
Environmental contamination with MRSA was found in approximately 1 in 6 objects in nursing home common areas. However, the frequency of contaminated objects varied across nursing homes. Two nursing homes had no positive cultures, while almost half of common area objects in another nursing home tested positive for MRSA. This variation indicates that certain facilities may have specific infection control strategies in place that effectively limit MRSA contamination and potential transmission between residents. Levels of environmental MRSA were significantly higher in nursing homes with greater differences in overall MRSA prevalence compared to imported levels, suggesting that contamination of fomites and surfaces in common areas may play a role in MRSA spread in nursing homes. Such contamination may be limited by improving cleaning practices in these areas.
We found that infection control practices, such as implementation of contact precautions for MRSA-positive residents, were not associated with MRSA contamination of common room objects. This evaluation may be limited by the relative homogeneity of certain practices in these ten nursing homes. In this study, 90% of nursing homes placed patients with MRSA infection on contact precautions. On the other hand, 80% did not restrict social interaction for residents who were only colonized, not infected, with MRSA. Further, criteria for discontinuation of contact precautions for residents with MRSA infection varied substantially, from completion of antibiotics to individual physician orders. Additional studies are needed to evaluate how infection control practices may be optimized to limit transmission without unduly hindering residents’ social activities and mental and physical well-being.
In contrast, we did find a significant association between MRSA contamination and cleaning practices. MRSA-positive objects were associated with the amount of time spent cleaning each room and with the frequency of common room cleaning. These measures are likely indicators of the thoroughness or quality of cleaning, which could impact whether MRSA is successfully removed from environmental sources. Increasing the time spent cleaning per room or the number of times common rooms are cleaned per day may be effective changes for nursing homes with significant MRSA transmission among residents. Studies directly assessing this question are needed.
Removal of cleaning marks from common areas was low and relatively uniform across nursing homes, where 1 in 5 marks were removed on average. Cleaning mark removal was similar between the low and high delta prevalence nursing home groups and was not correlated to levels of environmental MRSA. This finding may be partly due to the fact that cultures and marks were not always sampled from the exact same location on each object. More likely, mark removal in our investigation was uniformly poor (11–31% of marks removed across nursing homes) and below the threshold needed to demonstrate an association. It is possible that higher levels of mark removal of 70–100% may be needed to consistently remove MRSA from objects and surfaces, as previously shown.16
Similar to prior work, we found that cleaning was dependent on the type of object. As in other studies,16,21,23
objects with broad, flat surfaces (such as tables and counters) were more commonly cleaned. In contrast, objects with odd shapes or contours, such as chairs, handrails and doorknobs, were not cleaned as thoroughly or as often, although these objects are frequently touched.
We also found that persistence of cleaning marks was associated with higher MRSA admission prevalence, suggesting that cleaning may be insufficient in facilities that admit higher risk residents. This is worrisome since ideally cleaning measures would be more robust in nursing homes that admit a high fraction of residents carrying multi-drug resistant pathogens. These results suggest that cleaning-based interventions may need to focus training on high risk areas, objects, and even high risk nursing homes. Evaluating cleaning mark removal and providing feedback to environmental services staff has been shown to improve cleaning quality and reduce environmental contamination with MRSA and other multi-drug resistant pathogens in hospitals,16,22–23
and a similar approach may be effective in nursing homes.
Our study has several limitations. While a substantial difference in MRSA point and admission prevalence may result from transmission, we did not serially swab residents to determine if transmission actually occurred. Higher MRSA point prevalence may also result from unmasking of prior colonization, suggested by the association between having a history of MRSA and carriage of MRSA at point prevalence. Furthermore, our study of 10 nursing homes is limited by its sample size. Nevertheless, it is the largest study, to our knowledge, evaluating the association between MRSA prevalence among nursing home residents and environmental contamination. Our study also did not allow us to determine a causal relationship between these factors. We did not perform genetic testing of environmental MRSA strains; however, previous studies have shown that environmental MRSA strains are often highly genetically similar to strains carried by patients.28–30
Finally, we do not know the threshold of cleaning quality that must be achieved to reduce MRSA contamination, although our findings suggest that increasing the time spent cleaning per room and the frequency of common room cleaning may improve cleaning quality and reduce MRSA contamination levels. We were not able to determine which product is best for environmental cleaning, but this question may be an appropriate topic for future studies. Cleaning practices were obtained from surveys administered to environmental services staff, but were in agreement with on-site observations. While environmental contamination is only one possible reason for differences in MRSA prevalence in nursing homes, it may be particularly important in this setting due to the need for less stringent infection control policies. Moreover, environmental contamination represents a modifiable risk factor, since improved cleaning can reduce contamination levels.
In summary, we found that environmental MRSA contamination was highly variable among 10 nursing homes, and higher MRSA contamination levels among nursing home fomites were associated with a higher number of MRSA carriers at point prevalence versus admission prevalence, which may suggest that MRSA contamination contributes to transmission. Interventions to reduce environmental MRSA in nursing home should consider increasing the time spent cleaning per room and improving cleaning in common areas where residents routinely congregate.