An analysis conducted by the Centers for Disease Control and Prevention found a 28% drop in cases of MRSA contracted in hospitals from 2005 to 2008 and a 17% decrease in cases contracted outside the hospital but among people who had had kidney dialysis or had been in a hospital or nursing home in the prior year.
"We're very happy about this," said Dr. Ghinwa Dumyati, an associate professor of medicine at the University of Rochester Medical Center who directed one of the surveillance sites included in the study. "Hospitals have done a lot over the past decade to make care safer."
MRSA has been the most prominent of the infections that spread easily in hospitals. Though the Staphylococcus aureus bacterium is commonly found on skin and in the nose and is typically harmless, in cases of invasive MRSA — the focus of this study — it spreads to the blood, lungs, soft tissue, bones or joints.
The infection can progress rapidly, and is difficult to treat. An estimated 90,000 MRSA infections linked to healthcare are reported each year in the United States, causing about 15,000 deaths, mostly among older people or people with underlying illnesses.
Stringent infection-control strategies have been implemented in many hospitals, clinics and doctors' offices in the last decade to reduce infection rates. The measures include using routine checklists to ensure sterility, improved hand-washing, cleaning a patient's skin with disinfectant, removing unnecessary catheters and tracking infection rates.
Earlier small studies had hinted that infections were on the downswing. A study published last year found that cases of MRSA linked to catheter insertions in intensive care units had dropped substantially in the last decade, after following strict adherence to infection control procedures. Others have reported falling MRSA rates in Europe.
But the new report, published in the Journal of the American Medical Assn., is the most comprehensive analysis of MRSA trends in the U.S. to date. Using a surveillance system started in 2005, federal health officials gathered data on invasive MRSA from nine metropolitan areas. They found that healthcare-associated infections made up 82% of the 21,503 cases; the others, cases acquired in the community and unrelated to admissions to healthcare facilities, were not analyzed.
"We've seen slow, relentless increases of MRSA over time," said Dr. Alexander J. Kallen, a medical officer at the CDC and lead author of the study. "So we are very encouraged to see a substantial decrease."
Intense focus since 2000 on curbing hospital-acquired infections is probably a big factor in the decline, though it could have something to do with natural changes in the organism that causes it to emerge and then retreat, Kallen said.
The study also found a 19% drop in cases among people undergoing dialysis, a group that is especially vulnerable to MRSA infection, although that occurred from 2007 to 2008, slightly later than hospital rates began to fall. Infection-prevention efforts in outpatient healthcare settings may lag somewhat behind hospital initiatives, Kallen said.
The invasive MRSA problem is not over, University of Iowa infection-control experts emphasized in an editorial accompanying the study, and there are other dangerous bacteria that spread in healthcare settings.