Who is at risk for MRSA? New study identifies, quantifies and characterizes its prevalence

April 20, 2010, Lifespan

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 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 . Mermel is the medical director, department of epidemiology & infection control at Rhode Island Hospital.

In general, one in three individuals is colonized with Staphylococcus aureus, most often involving the . 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 , respectively, carried nasal MRSA, as did 16% of 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."

The researchers also found different strains of MRSA in different patient populations. For example, while USA100 was the most common MRSA strain detected, the USA 300 strain was much more commonly found in HIV-infected patients. The researchers also detected some MRSA strains not previously identified in the US, such as an MRSA clone common in Brazil.

Mermel and his colleagues also found dramatic diversity in the quantity of MRSA colonizing the noses of people. Some people had as few as 3 colonies of MRSA in their nose detected with a nasal swab whereas others had as many as 15 million colonies of MRSA. Mermel notes, "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 says the study findings identify patient populations at increased risk for MRSA carriage and . Future studies can use this information to determine a biologic explanation for differences in strains and quantities of MRSA that some people carry in their noses.

Related Stories

Recommended for you

Past encounters with the flu shape vaccine response

February 20, 2018
New research on why the influenza vaccine was only modestly effective in recent years shows that immune history with the flu influences a person's response to the vaccine.

Building better tiny kidneys to test drugs and help people avoid dialysis

February 16, 2018
A free online kidney atlas built by USC researchers empowers stem cell scientists everywhere to generate more human-like tiny kidneys for testing new drugs and creating renal replacement therapies.

Study suggests expanded range for emerging tick-borne disease

February 16, 2018
Human cases of Borrelia miyamotoi, a tick-borne infection with some similarities to Lyme disease, were discovered in the eastern United States less than a decade ago. Now new research led by the Yale School of Public Health ...

Expanding Hepatitis C testing to all adults is cost-effective and improves outcomes

February 16, 2018
According to a new study, screening all adults for hepatitis C (HCV) is a cost-effective way to improve clinical outcomes of HCV and identify more infected people compared to current recommendations. Using a simulation model, ...

Flu shot only 36 percent effective, making bad year worse (Update)

February 15, 2018
The flu vaccine is doing a poor job protecting older Americans and others against the bug that's causing most illnesses.

IFN-mediated immunity to influenza A virus infection influenced by RIPK3 protein

February 15, 2018
Each year, influenza kills half a million people globally with the elderly and very young most often the victims. In fact, the Centers for Disease Control and Prevention reported 37 children have died in the United States ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.