A multi-center study led by a researcher at Rhode Island Hospital has determined that long-term elder care, HIV-infected and hemodialysis patients are at increased risk of carrying methicillin-resistant Staphylococcus aureus (MRSA) in their nose. The study also found that patients have vastly different quantities of MRSA in their noses, a potential indicator for their risk of developing an infection after surgery. The study appears in the June 2010 edition of the journal Infection Control and Hospital Epidemiology and appears online in advance of print.
In order to better understand the prevalence of MRSA in different patient populations, lead author Leonard Mermel, DO, ScM, worked with researchers at The Cleveland Clinic, Johns Hopkins Medical Institutions, Emory University and other organizations to obtain specimens from the noses of a variety of patients. Mermel is the medical director, department of epidemiology and infection control at Rhode Island Hospital.
In general, one in three individuals is colonized with Staphylococcus aureus, most often involving the nose. In the US, approximately 1 percent of people carry MRSA in their nose. Carrying MRSA in the nose increases the risk of developing an invasive MRSA infection such as bloodstream infection, pneumonia, surgical site infection, etc.
Staphylococcus aureus is the second most common pathogen causing health care-associated infections in the United States, and 49 percent of those infections are caused by the highly antibiotic-resistant bacteria MRSA. A strain called USA100 is the most common type of MRSA involved in health care-associated infections in U.S. hospitals.
In this study, 444 nose cultures of 2,055 patients from 13 enrollment centers resulted in growth of MRSA. The researchers found that 14 percent and 15 percent of inpatient and outpatient hemodialysis patients, respectively, carried nasal MRSA, as did 16 percent of HIV infected patients, and 20 percent of long-term elder care residents. Based on these findings, Mermel, who is also a professor of medicine at The Warren Alpert Medical School of Brown University and a physician with University Medicine, recommends, "Hospitals performing active surveillance for MRSA should consider such patient populations for screening cultures."