Some U.S. hospitals appear to be making progress in curbing the incidence of a drug-resistant staph infection among their sickest patients, researchers say.

Antibiotic-resistant strains known as methicillin-resistant staphylococcus aureus, or MRSA, cause serious and costly infections. A hospital patient who develops an MRSA infection can expect the length of his or her hospital stay to triple.

'Despite this progress, most ICUs are far from the goal of zero infections and many have not implemented suggested prevention strategies.'— Dr. Michael William Climo

There's a public perception that patients in intensive care are at greatest risk for contracting MRSA because staff often use central lines that can provide MRSA with a direct path into a patient's bloodstream.

In Wednesday's issue of Journal of the American Medical Association, Dr. Deron Burton of the Centers for Disease Control and Prevention in Atlanta and colleagues analyzed national surveillance data collected from almost 600 hospitals between 1997 and 2007 to test that assumption by tracking the risk of MRSA infections in ICUs.

"Doctors often use catheters inserted into major blood vessels both for treatment and monitoring," said Burton.

"These catheters, which are sometimes called central lines, are vital for patient care, but they also can represent a potential source for infection of the bloodstream with MRSA or other microorganisms."

From 1997 to 2001, in four of the seven major types of ICU studied, the risk was increasing, Burton said.

But since 2001, the risk of MRSA infections in the bloodstream associated with the use of a central line in ICUs decreased by roughly 50 per cent — in medical-surgical ICUs without a major teaching affiliation — to nearly 70 per cent — in surgical ICUs.

"In summary, MRSA central line–associated BSI [bloodstream infections] incidence has declined in recent years in all major adult ICU types and has remained stable in pediatric ICUs," the researchers concluded.

Don't let guard down

The study's authors found 1,684 intensive care units reported a total of 33,587 blood infections caused by central line catheters during the study period.

Of those, 2,498, or about 7 per cent, were drug-resistant strains of MRSA, and 1,590, or 4.7 per cent, were staph infections that were susceptible to antibiotics

The percentage of MRSA infections in proportion to infections that are susceptible to antibiotics went up over the same time period that the actual incidence of MRSA declined. That discrepancy potentially contributed to the perception that the problem has increased, the researchers said.

It's important for hospitals to use both measurements, proportion and incidence, to get a true picture of how well the infections are handled, the study's authors said.

The emergence of MRSA in health care settings has prompted calls for mandatory screening or reporting, and hospitals have been working on improving the safety of central line use, particularly in intensive care units, the researchers said.

In an editorial accompanying the study, infectious disease specialist Dr. Michael William Climo of the Hunter Holmes McGuire Veterans Affairs Medical Center in Richmond, Va. said the study shows ICUs participating in the surveillance program have made progress at reducing hospital infections.

"Despite this progress, most ICUs are far from the goal of zero infections and many have not implemented suggested prevention strategies," Climo said.

Hospitals should continue to use well-researched prevention strategies, he added.

Rates of MRSA in Canada more than doubled in the period from 1999 to 2005, according to a study published in the American Journal of Infection Control in December 2008 that surveyed hospitals with 80 or more beds.

Outbreaks of MRSA have also occurred in schools and other community settings.