WASHINGTON – More people are acquiring methicillin-resistant Staphylococcus aureus (MRSA) outside of hospitals, bringing the bacteria into outpatient settings and increasing hospitals' burdens in fighting the deadly bug, a study shows.

MRSA has increased seven-fold among hospital outpatients who have "community-associated " strains, according to the study published in the December issue of Emerging Infectious Diseases. Researchers said "community-associated" MRSA is easily picked up in fitness centers, schools, and other public places and has increased the overall burden of MRSA within hospitals.

To curtail the spread of MRSA from its outpatients to its inpatients, hospitals should step up infection control procedures, including those practiced in outpatient units, authors of the study said. This study and others suggest that the most effective way of containing MRSA and other superbugs is by employing surveillance and infection control on a regional basis.

"The movement of community-associated strains into the hospital also points to the urgent need for rapid tests that can identify the strain of MRSA," according to Eili Klein, the report's lead author and researcher at Resources for the Future.

Some MRSA strains, particularly those coming into the outpatient departments, are vulnerable to a wider range of cheap antibiotics. With a rapid test, a hospital doctor could prescribe a cheaper, but still effective drug to combat an infection-a strategy that might reduce healthcare costs and help preserve the nation's supply of antibiotics, Klein said.

According to the Centers for Disease Control and Prevention (CDC), about 20,000 people in the United States die each year from MRSA. There are more than 63,000 deaths each year associated with hospital-acquired infections resistant to at least one antibiotic - more deaths than from AIDS, traffic accidents, or influenza.

The additional cost of treating an antibiotic-resistant staph infection ranges from $3,000 to more than $35,000 per case, according to CDC.

The study analyzed data from more than 300 microbiology laboratories serving hospitals all over the United States between 1999 and 2006.

According to study authors, the increased numbers of patients with MRSA who arrive with the bacteria at the hospital, rather than acquiring it at the hospital, has also increased threats to patient safety because doctors and patients often move back and forth between inpatient and outpatient units.

"This emerging epidemic of community-associated MRSA strains appears to add to the already high MRSA burden in hospitals," said Ramanan Laxminarayan, principal investigator for Extending the Cure, a project that examines policy solutions to the growing problem of antibiotic resistance based at the Washington, D.C. think-tank Resources for the Future.

Over the length of the study, researchers found that the proportion of MRSA increased more than 90 percent among outpatients with staph and now accounts for more than 50 percent of all Staphylococcus aureus infections.

The findings suggest that this was due almost entirely to an increase in community-associated strains, which jumped from 3.6 percent of all MRSA infections to 28.2 percent-a seven-fold jump from 1999 to 2006. Similar increases in inpatients suggest that these strains are spreading rapidly into hospitals as well.