Virulent Strain of MRSA Resists Treatment

(HealthDay News) -- New research holds bad news for health officials worried about a potentially lethal infection called MRSA that haunts hospitals: A strain that infects the bloodstream is five times more deadly than other strains.

To make matters worse, the USA600 strain appears to be at least partially immune to an antibiotic that's used to treat the condition, the researchers have found.

A full half of patients infected with the strain died within a month, according to a study scheduled to be presented at the annual meeting of the Infectious Diseases Society of America, held Oct. 29 to Nov. 1 in Philadelphia. That's nearly five times the death rate of other people infected with MRSA, and 10 to 30 percent of those who acquire MRSA infections in the bloodstream die within a month, the study found.

MRSA, or methicillin-resistant Staphylococcus aureus, causes infections in the skin and bloodstream. It can also infect surgical wounds and cause pneumonia. In most cases, it sickens people in the hospital, but cases are becoming more common outside the health-care community, according to information in a news release from the Henry Ford Health System.

Researchers think it's possible that the USA600 strain is unique. But they don't know if other factors -- such as the age of patients -- could be at play.

Those who developed the USA600 strain tended to be older than those who acquired other MRSA strains, averaging 64 compared with 52 years old, the study noted.

"While many MRSA strains are associated with poor outcomes, the USA600 strain has shown to be more lethal and cause high mortality rates," Dr. Carol Moore, the study's lead author and a research investigator at the Henry Ford Hospital's division of infectious diseases, said in the news release.

"In light of the potential for the spread of this virulent and resistant strain and its associated mortality," she said, "it is essential that more effort be directed to better understanding this strain to develop measures for managing it."

MRSA is challenging to treat because strains can be immune to many medications. The USA600 strain appears to be more immune than other strains to the drug vancomycin, which often still has the power to vanquish MRSA.

SOURCE: Henry Ford Health System, news release, Oct. 31, 2009