Doubt cast on effectiveness of universal MRSA screening

The struggle to limit the spread of methicillin-resistant Staphylococcus aureus in hospitals just got a little more complicated.

Some research has supported the screening of all patients admitted to intensive care units for MRSA and taking additional infection-control precautions if they are colonized or infected. Lawmakers in 10 states, alarmed about the rising incidence of MRSA in the last decade, have mandated that hospitals implement this costly "active surveillance" approach.

But it's not that simple, according to a study published April 14 in The New England Journal of Medicine (link). Researchers screened more than 5,400 patients at 10 ICUs for MRSA and vancomycin-resistant enterococcus, asking health professionals to clean their hands, wear gloves and don gowns when entering the rooms of any colonized or infected patients. The control efforts also were implemented for any patients colonized or infected in the year before admission.

For comparison purposes, researchers tracked more than 3,700 admissions to eight ICUs that did not implement active surveillance.

After six months, there was no difference in the MRSA or VRE colonization or infection rates between the two groups of ICUs despite the added screening and prevention measures.

"We were surprised by the result," said W. Charles Huskins, MD, lead author of the study and a consultant in pediatric infectious diseases at the Mayo Clinic in Minnesota. "There was something missing in terms of the intervention."

Two factors may have limited the efficacy of the active surveillance, Dr. Huskins said. All nasal swabs were sent to the National Institutes of Health's Clinical Microbiology Laboratory for culture testing, creating a five-day wait that delayed implementation of the added infection-control measures. Also, adherence to the hygiene standards was less than perfect. Health professionals wore gloves 82% of the time they interacted with colonized or infected patients, donned gowns 77% of the time and cleaned their hands 69% of the time after leaving patient rooms.

MRSA's complications

The study casts doubt on the wisdom of mandating MRSA screening, Dr. Huskins said.

"I don't think a strategy like what we implemented is likely to be broadly effective or yield an across-the-board, one-size-fits-all approach," he said. "When you write a law, it's a one-size-fits-all approach."

Another study in the same issue of NEJM found that active surveillance included as part of a group of interventions implemented nationwide at Veterans Affairs hospitals reduced the MRSA infection rate by 62% from 2007 to 2010 (link).

The study of nearly 2 million ICU admissions is not directly comparable to Dr. Huskins' study because there was no control group. Also, the VA implemented other measures, such as guidelines for ventilator-associated pneumonia and central line-associated bloodstream infections, that could have contributed to the declining MRSA infection rate.

MRSA kills about 18,000 people annually, according to the Infectious Diseases Society of America.