We've been hearing for some time now about the proliferation of drug-resistant staph infections caused by bacteria that are stronger than antibiotics. Today there's an indication that in at least one small portion of the universe, the infections are actually on the decline.

The rate of methicillin-resistant Staphylococcus aureus (MRSA) bloodstream infections from central lines (intravenous catheters) in hospital intensive care units (ICUs) dropped by half between 1997 and 2007, according to research in tomorrow's Journal of the American Medical Association (JAMA). It’s unclear exactly how many Americans become sick with MRSA in ICUs every year, but an estimated 94,360 Americans contracted such infections in 2005, just over a quarter of them caught in the hospital, according to CDC research published two years ago in JAMA. MRSA is responsible for 5.6 percent of all central line-caused infections.

So it’s good news, but there are a few catches: If you do catch a staph infection in the ICU, it was still more likely during the time period studied that you’d have MRSA, rather than the much more treatable methicillin-susceptible Staphylococcus aureus (MSSA).

Nor does the research, by Centers for Disease Control and Prevention (CDC) researchers, speak to the chance of catching MRSA elsewhere in the hospital — never mind outside, which is where experts say the problem is worst.

"This is just a subset of the problem and we can't use it to speak to the whole problem," says study co-author Deron Burton, a lieutenant commander in U.S. Public Health Service. "But we are seeing success in reducing MRSA risk, because while ICU patients are smaller in number, they are highly vulnerable. To see we've had dramatic decline in high-risk patients is a very exciting finding about what's happening with MRSA in the healthcare facility."

Burton added that the data doesn’t make clear why MRSA is more common in the ICU than MSSA. Overuse of antibiotics has been speculated as a possible cause.

Hospitals in recent years have tried to reduce bloodstream infections by implementing more standardized hand-washing procedures for staff, methods of inserting catheters and taking them out sooner. But the study doesn’t show which of these infection-control methods, if any, accounted for the decline in staph and other bloodstream infections in the ICU, wrote Michael William Climo of the Hunter Holmes McGuire VA in Richmond, Virginia, in an editorial accompanying the study.

What's more, fewer than 6 percent of ICUs that submitted data to the National Healthcare Safety Network, a voluntary surveillance system that monitors the infections, contributed data for the whole length of the study. And it's unknown whether MRSA bloodstream infections transmitted through ventilators, or those in the skin and soft tissue, also decreased among those hospitals.

"Clearly, ICUs … have made substantial progress at reducing hospital-acquired infections, suggesting that real change is being made," Climo wrote. "Despite this progress, most ICUs are far from the goal of zero infections."

Image of MRSA/CDC/Janice Haney Carr/Jeff Hageman via Public Health Image Library