UR, Monroe County Help Paint National Picture of Falling MRSA Rates

Aug. 10, 2010

National health care efforts to curb the spread of the dangerous bacterial infection MRSA seem to be paying off, according to new research published today in the Journal of the American Medical Association.

The findings, which come from the Centers for Disease Control and Prevention (CDC), show that the number of health care-associated MRSA cases has fallen upwards of 17 percent between 2005 and 2008 in nine communities across the country. The study represents one of the largest U.S. populations evaluated for changes in incidence of severe MRSA infections in recent years.  

The University of Rochester (UR) is at the forefront of helping track these infections, as UR infectious disease physician and Monroe County epidemiologist Ghinwa Dumyati, M.D., led local CDC efforts tracing MRSA cases county-wide for the four-year study. The New York/Monroe County surveillance site – one of only nine communities studied and one of ten sites in the CDC's Emerging Infections Program (Active Bacterial Core) – represents a partnership between the University of Rochester School of Medicine & Dentistry and the Monroe County Department of Public Health.

MRSA bacteria, magnified more than 9,500 times. (Courtesy of the CDC's Public Health Image Library)

“The study pools data from diverse geographic areas encompassing almost 15 million residents,” said Dumyati, an associate professor of Medicine at the University of Rochester who directs communicable disease, immunization and vaccine efficacy studies at University’s Center for Community Health. “Preventing these infections is a national priority. While the numbers undoubtedly show we’ve made progress, more work remains.”

Each year, an estimated 1.7 million health care-associated infections plague the U.S., with 99,000 ending in death at U.S. hospitals. MRSA, or methicillin-resistant Staphylococcus aureus, is among the prime offenders.

For this study, researchers focused on health care-associated MRSA cases, dividing them into two groups: hospital-onset infections, versus community-onset infections occurring after patients were discharged, or after they received care in an outpatient setting, like a dialysis center. Cases were confirmed after a laboratory report of a positive MRSA culture.

Ghinwa Dumyati, M.D.

By 2008, the nine sites on average had witnessed the rates of health care-associated MRSA infections fall dramatically. Specifically, infections on average dropped 28 percent amongst patients in hospitals, and 17 percent amongst those patients whose infections developed in the community after a recent health care contact.

“This is welcome news, especially after a 2006 CDC report that the number of staph infections resistant to methicillin had more than doubled between 1999 and 2005,” Dumyati said. “These newest numbers are certainly trending in the right direction.” 

What makes an infection of MRSA especially troublesome is that the bacterium has developed immunity to the very antibiotics used to kill it.

“At the start of the decade, this type of bacteria was just mushrooming,” Dumyati said. “Many came to refer to it as a ‘superbug.’”

In the community, MRSA infections usually affect the skin, resembling pimples or spider bites that can quickly deteriorate into oozing abscesses. But in health care setting like hospitals and nursing homes – where most severe infections originate – MRSA is more than skin-deep. Most infections occur after a patient receives a catheter, undergoes surgery, or receives another intervention that affords bacteria a prime opportunity to bypass the body’s protective armor: the skin. From there, the bacteria can potentially inflict life-threatening damage to the bones, joints, surgical sites, the bloodstream, heart valves and lungs.

In recent years, health care organizations have mobilized to step up efforts to prevent the disease’s spread, often fighting the battle on several fronts.

 “At the moment, we can’t pinpoint any one particular tactic that’s most responsible,” she said. “But we suspect a big part of our success nationally is spillover benefit of our hard work in preventing the transmission of MRSA in the hospitals and reducing infections in central lines.”

Central lines – or soft tubes that carry hydration, medicine and food right into major veins – are life-saving tools, but place patients at greater risk for infection. In fact, about 85 percent of all health care-associated MRSA cases are bloodstream infections, many of which researchers expect are due to central lines. Recently however, as hospitals have become more deliberate about creating line-care ‘bundles’ – specific directives for line insertion and maintenance that need to be followed precisely – the subset of MRSA infections affecting the bloodstream dropped considerably (even more dramatically than health care-related MRSA infections dropped overall). Over the four-year study, the number of bloodstream MRSA infections that began in the hospital fell 34 percent; those occurring in the community (after health care contact) fell by about 20 percent.

In spite of this progress, big questions remain. Dumyati is currently involved in research to better understand the risk factors that contribute to community-onset infection after a patient leaves a health care setting.

To learn more about CDC’s Emerging Infections Program and its mission, click here. To hear Dumyati discuss the study in more detail, click here.