[Methicillin-resistant Staphylococcus aureus: evolution and epidemiology, clinical impact, and prevention]

Methicillin-resistant Staphylococcus aureus (MRSA) strains have become endemic in hospitals in many countries. In most cases, epidemic clones emerge occasionally on the endemic background. Early institution of simple measures aimed at preventing hand-borne cross-contamination has resulted in low rates of MRSAs in a few countries of northern Europe. Although environmental contamination plays a role in some cases, colonized or infected patients are the main reservoir. Three significant problems have been identified in countries with high levels of endemicity, namely identification of the reservoir in the hospital, including detection of healthy carriers who are readmitted; notification of departments that receive healthy carriers transferred from another department in the same hospital or from another hospital; and the increasing and hard-to-control reservoir of resistant bacteria in extended-care facilities. These three problems are related to the current level of endemicity and to the risk of dissemination of resistant strains during hospital-to-hospital patient transfers. The technical responses to these problems vary with the environment and available means. They include detection of carriers in high-risk units, use of standardized reporting forms for patient transfers, and recording of the presence of MRSA in computerized medical records. Decontamination of carriers can help to prevent cross-contamination in some situations. It is of the utmost importance that all the facets of MRSA endemicity be taken into account at the level of the hospital as a whole and that all decision makers and health care providers make a commitment to reducing MRSA endemicity.