People who live near livestock or in livestock farming communities may be at greater risk of acquiring, Methicillin-resistant Staphylococcus Aureus (MRSA), according to a new study led by an international team of researchers from the Johns Hopkins Bloomberg School of Public Health, the Dutch Institute for Public Health and the Environment (RIVM) and VU University Medical Center in Amsterdam. A comparison of livestock density, place of residence and existing information on risk factors found that regional density of livestock is an important risk factor for nasal carriage of livestock-associated (LA) MRSA for persons with and without direct contact with livestock. The results are featured in the November issue of Emerging Infectious Diseases.
Staphylococcus aureus is a pathogen that can cause a range of illnesses in humans, from minor to life-threatening skin, bloodstream, respiratory, urinary and surgical site infections. According to the Centers for Disease Control and Prevention, MRSA is a type of staph bacteria that is resistant to penicillin and certain first-line antibiotics called beta-lactams. MRSA infections are most commonly infections of the skin. Though nasal carriage, the indicator under study in this research, does not indicate that someone is infected with MRSA, it is associated with increased risks of eventual infection. Moreover, in this study it is a measure of exposure to MRSA. "In the past, MRSA has been largely associated with hospitals and other health care facilities, but in the last decade the majority of infections have been acquired in the community outside of a health care setting," said Ellen Silbergeld, PhD, co-author of the study and a professor with the Bloomberg School of Public Health's Department of Environmental Health Sciences.
This study is the first to suggest the importance of indirect routes of transmission of livestock-associated MRSA. Jan Kluytmans, MD, PhD, co-author of the study and professor of Medical Microbiology and Infection Control, VU University Medical Center Amsterdam and Amphia Hospital Breda, the Netherlands, said, "In the Netherlands LA-MRSA was first found in 2003 and was initially almost exclusively found in persons with direct contact to livestock. In recent years LA-MRSA is found with increasing frequency in community-dwelling individuals with no known contact with livestock. It is important to determine the routes of transmission outside of the farms since this may have important consequences for public health."