Screening all incoming hospital patients for methicillin-resistant Staphylococcus aureus (MRSA) and isolating those infected did nothing to prevent its spread, new Swiss research shows.

Dr. Stephan Harbarth and colleagues with the University of Geneva Hospitals and Medical School in Switzerland conducted a study to evaluate the effect of an early detection strategy on MRSA infections acquired in a hospital among 21,754 surgical patients at a Swiss teaching hospital.

The study found screening did not reduce the number of patients who caught the infection during their hospital stays and was not cost effective. Roughly, 85 percent of MRSA cases, which is treatable only with a few antibiotics, occur in hospitals, where infection can kill weakened patients.

Some 93 patients developed MRSA in the screening group - 1.11 per 1,000 patient days - compared to 76 - 0.91 per 1,000 patient days - in the control group.

"It wasn't what we expected. We were very surprised. The trial did not show an added benefit for widespread rapid screening on admission compared with standard MRSA control alone. To increase effectiveness, MRSA screening could be targeted to surgical patients who undergo elective procedures with a high-risk of MRSA infection,” said lead author Dr. Stephan Harbarth in the study.

The finding -- described by the Swiss researchers as "worrisome" -- came as several U.S. states are mandating the use of active surveillance cultures as routine screening for MRSA. The bacterium can lead to skin and blood infections and pneumonia.

”It remains to be seen whether a strategy combining early detection, preemptive isolation, and intense promotion of basic infection control measures might be more successful," the researchers added in their study.

The findings appeared in the March 12 issue of the Journal of the American Medical Association.

According to a related editorial in the same issue of the journal, one-quarter of U.S. hospitals reported at least one MRSA outbreak in the prior year. In addition, an estimated 18,000 or more deaths could be attributable to invasive MRSA infections in the United States in 2005. More than 4 million individuals in the United States may be carriers of the pathogen, and as many as 1.2 million U.S. hospital patients may be infected each year with MRSA.