Study establishes baseline for MRSA infection estimates

Methicillin–resistant staph aureus (MRSA) caused more than 94,000 life–threatening infections and nearly 19,000 deaths in the United States in 2005, most of them associated with health care settings, according to the most thorough study of life–threatening infections caused by these bacteria, experts with the Centers for Disease Control and Prevention (CDC) report.

The study in the Oct. 17 edition of the Journal of American Medical Association (JAMA) establishes the first national baseline by which to assess future trends in invasive MRSA infections. MRSA infections can range from mild skin infections to more severe infections of the bloodstream, lungs and at surgical sites.

The study found about 85 percent of all invasive MRSA infections were associated with health care settings, of which two–thirds surfaced in the community among people who were hospitalized, underwent a medical procedure or resided in a long–term care facility within the previous year. In contrast, about 15 percent of reported infections were considered to be community–associated, which means that the infection occurred in people without documented health care risk factors.

The 2005 rates of invasive infection were highest among people 65 years of age or older. Black people were affected at twice the rate of whites, which could be due to higher rates of chronic illness among blacks.

“These numbers show that many families are being affected by these drug–resistant infections,” said Denise Cardo, M.D., director of CDC′s Division of Healthcare Quality Promotion. “Healthcare facilities need to make MRSA prevention a greater priority. The closer we get to 100 percent compliance with CDC recommendations, the greater the impact on patient health and safety.”

Experts arrived at the new national estimate by projecting from the number of invasive MRSA cases from nine U.S. sites. The sites included the state of Connecticut; the Atlanta metropolitan area; the San Francisco Bay area; the Denver metropolitan area; the Portland, Ore., metropolitan area; Monroe County, N.Y.; Baltimore City, Md.; Davidson County, Tenn.; and Ramsey County, Minn. All the sites were part of CDC′s Active Bacterial Core surveillance program, which actively tracks a number of pathogens in the United States representing a population of 38 million Americans.

In health care settings, MRSA occurs most frequently among patients who undergo invasive medical procedures or who have weakened immune systems and are being treated in hospitals and health care facilities such as nursing homes and dialysis centers.

For more information on MRSA, please visit http://www.cdc.gov/ncidod/diseases/submenus/sub_mrsa.htm. For more information on CDC′s guidelines for the prevention of MRSA in health care settings, visit http://www.cdc.gov/ncidod/dhqp/ar_mrsa_prevention.html.