From 2005 to 2008, the rate of MRSA (methicillin-resistant Staphylococcus aureus) infections dropped by almost 28% among hospitalized patients and 17% among people who were not hospitalized but acquired the infection following medical procedures like dialysis.
The figures are based on an analysis of data from nine metropolitan areas across the U.S.
The CDC estimates that about 1.7 million health-care-related infections occur annually in the U.S., resulting in 99,000 deaths.
Multidrug-resistant MRSA infections have been among the most deadly, killing thousands of people each year.
The latest analysis is based on data obtained from the CDC's Emerging Infections Program/Active Bacterial Core surveillance system and represents the largest attempt to track infection rates across the country.
The research appears in the Aug. 11 issue of the Journal of the American Medical Association.
"This is really good news," CDC medical officer Alexander J. Kallen, MD, who led the study, tells WebMD. "It suggests interventions aimed at reducing infections in health care settings are having an impact. But much more needs to be done."
Health-care-related exposures were responsible for 82% of all MRSA infections identified in the analysis.
Overall, the nine surveillance sites reported 21,503 invasive cases of MRSA from 2005 through 2009, with just over 17,500 classified as health care-related.
The biggest declines during the period were seen in the most deadly MRSA infections -- those that invaded the bloodstream. Bloodstream infections dropped by about 34% among hospitalized patients and 20% among other health care-related exposures during the four-year study period.
Increased Infection-Control Efforts
Last year, a CDC analysis of catheter-related MRSA bloodstream infections occurring in intensive care units, which are tracked nationally, also showed a significant decline in cases.
Taken together, the two studies suggest a real decline in MRSA infections in U.S. hospitals, Kallen says.
The reason for the drop is not so clear. Greater awareness of the dangers of MRSA and other hospital-acquired infections has led most hospitals to step up their efforts to control the spread of pathogens in their facilities.
But there is debate within the infection-control community about whether conventional infection-control efforts or MRSA-specific efforts have had the most impact.
General infection-control strategies include stressing hand hygiene -- frequent hand washing and use of alcohol-based hand rubs -- to hospital staffers as well as keeping catheters and other invasive medical devices free of infection.
MRSA-specific interventions involve testing patients for the multidrug resistant staph infection during hospital admission and isolating those who test positive.
In an editorial published with the CDC report, University of Iowa health practices researcher Eli Perencevich, MD, wrote that the impact of these strategies may never be fully understood, since close to one in three people is colonized with Staphylococcus aureus.
"It may be presumptuous to assume that hospital-based infection prevention efforts have a major effect on the natural history of a pathogen that colonizes up to a third of humans," he and colleague Daniel J. Diekema, MD, write. "Natural biological trends, including the emergence and disappearance of specific clones, are likely to override the best-laid attempts at infection control."
But in an interview with WebMD, Perencevich said both general and MRSA-specific infection-control efforts are probably having an impact on the overall downward trend in infections.
"There is no debate about the importance of general infection control, such as stressing hand hygiene and adequately inserting and caring for central venous catheters," he says. "But we need to expand surveillance beyond these nine sites to give us a better picture of what is happening nationwide."