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New Study Says Two Million Americans Harbor Drug-Resistant Superbug

December 22, 2005

New research estimates that about 2 million people carry a strain of drug-resistant bacteria in their noses. The research, conducted by the Centers for Disease Control and Prevention (CDC), is the first reliable nationwide estimate of colonization with Staphylococcus aureus, including methicillin-resistant Staphylococcus aureus (MRSA). It is published in the Jan. 15 issue of The Journal of Infectious Diseases, now available online.

Those colonized with normal strains of staph are at higher risk of infection with the bacterium, which can lead to conditions ranging from mild skin infections to fatal toxic shock syndrome. MRSA causes more difficult-to-treat and, sometimes, more virulent illnesses. MRSA was once primarily a problem in hospitals, but is now a growing problem in communities around the country.

Matthew J. Kuehnert, MD, and colleagues collected samples from nearly 10,000 participants in the 2001-2002 National Health and Nutritional Examination Survey, a representative sample of the U.S. population.

Nearly one-third were found to be colonized with staph. Prevalence was highest among males and children between 6 and 11 years old. MRSA prevalence was 0.8 percent. MRSA was highest among women and those older than 60, but those colonized with strains commonly associated with community-associated MRSA were more likely to be younger and black.

Overall, strains and toxins previously found to be associated with community-associated MRSA were unusual. The genetic diversity of strains was remarkable-about half of isolates, including MRSA strains, had unique molecular fingerprinting patterns, and some fell outside recognized groups.

"There is a lot about staph colonization we don't know," Dr. Kuehnert said. "Interestingly, carriage of certain strains do seem to vary by sociodemographics, especially age and race. We need to learn more in order to allow design of new, more effective interventions," he added, including vaccines or antimicrobial treatment. "Data from subsequent survey years may determine whether there are ongoing trends in colonization."

In an accompanying editorial, Clarence Buddy Creech II, MD, of Vanderbilt University and colleagues observe that, "In light of the increasing frequency of community-associated MRSA infection, new antimicrobials are needed," although an effective vaccine against staph would provide a more permanent solution.

The Journal of Infectious Diseases