MRSA carriage rates vary widely in nursing homes, study finds

December 1, 2010

A study published in the January 2011 issue of Infection Control and Hospital Epidemiology finds that a high percentage of nursing home residents carry Methicillin-resistant Staphylococcus aureus (MRSA), and suggests that some nursing homes could be doing more to prevent the spread of the bacteria, which can lead to hard-to-treat infections.

The study, which looked at 10 nursing homes in Orange County, California, found that 31 percent of the residents who were tested were carrying MRSA (meaning they could pass the bacteria along to others, but were not necessarily sick with infection). That rate is substantially higher than rates found in hospitals and even intensive care units, according to Susan Huang, medical director of epidemiology and infection prevention at the University of California Irvine Medical Center and one of the study’s authors.

The study also found, however, that carriage rates in each of the individual facilities in the study varied widely, from a high of 52 percent in one facility to a low of 7 percent in another.

“The high overall levels of MRSA are reason for concern,” Huang said. “But the variation in rates between facilities may be good news because it suggests some facilities are finding effective ways to contain the bacteria.”

Nursing homes have long been considered high risk facilities for MRSA infections. However, few studies have compared multiple facilities in one area to look for variation in MRSA carriage.

The researchers took nasal swabs from a sample of 100 residents in each of the 10 homes. They also took samples from 50 people at each home at the time they were admitted to get an idea of how much MRSA was coming into each facility.

The study found that a nursing home’s rate of MRSA carriage was not simply a result of how much MRSA came in with new residents, and suggests that some homes do a better job than others of containing the bacteria once it arrives. For example, two nursing homes in the study had identical MRSA intake rates of 12 percent, but one of those homes had an overall MRSA carriage among its established residents of 22 percent, while the other had a rate of 42 percent.

The next step, Huang said, is to find out exactly what these facilities are doing to better contain MRSA.

“The social environment in a nursing home has a positive influence on residents, who are encouraged to frequently mingle,” Huang said. “We don’t want to stymie that residential feel which can be very important to mental and physical health, but we think there’s more to be learned about what nursing homes can do to contain MRSA.”