MRSA More Likely to Lurk in Certain Patients

FRIDAY, April 23 (HealthDay News) -- Certain patients are far more likely than others to carry methicillin-resistant Staphylococcus aureus (MRSA), in their noses, a new study shows.

Although they are not infected with the potentially lethal germ, its mere presence heightens their risk of developing MRSA-related pneumonia, bloodstream infection and surgical site infection, the research concludes.

In the United States, about 1 percent of people carry MRSA in their nose. But this study of 2,055 patients found that MRSA was present in the noses of 20 percent of long-term elder care patients, 16 percent of HIV-infected patients, and 14 percent and 15 percent of inpatient and outpatient kidney dialysis patients.

"Hospitals performing active surveillance for MRSA should consider such patient populations for screening cultures," study author Leonard Mermel, medical director of the department of epidemiology and infection control at Rhode Island Hospital, said in a news release.

USA100 -- a health care-associated MRSA strain -- was the most common MRSA strain detected in patients, but a more virulent community-associated strain known as USA300 was much more commonly found in HIV-infected patients, the researchers noted. They also detected some MRSA strains not previously identified in the United States, including an MRSA clone common in Brazil.

There were huge differences in the number of MRSA colonies in the noses of the patients in the study. Some had as few as three colonies of MRSA while others had as many as 15 million colonies.

"This finding is important because heavy MRSA colonization of the nose is an independent risk factor for the development of a surgical site infection," Mermel said.

Further research is needed to learn why people have different strains and quantities of MRSA in their noses, Mermel said.

The study appears online and in the June print issue of the journal Infection Control and Hospital Epidemiology.

More information

The U.S. Centers for Disease Control and Prevention has more about MRSA.