• Jesús Rodríguez-Baño, Lola García, Encarnación Ramírez, Carmen Lupión, Miguel A Muniain, Carmen Velasco, Juan Gálvez, M Dolores del Toro, Antonio B Millán, Lorena López-Cerero, and Alvaro Pascual.
• Sección de Enfermedades Infecciosas, Servicio de Microbiología, Hospital Universitario Virgen Macarena, and the Departamento de Medicina, Universidad de Sevilla, Sevilla, Spain. jesusrb@us.es
• Infect Control Hosp Epidemiol. 2010 Aug 1;31(8):786-95.

ObjectiveTo evaluate the long-term impact of successive interventions on rates of methicillin-resistant Staphylococcus aureus (MRSA) colonization or infection and MRSA bacteremia in an endemic hospital-wide situation.DesignQuasi-experimental, interrupted time-series analysis. The impact of the interventions was analyzed by use of segmented regression. Representative MRSA isolates were typed by use of pulsed-field gel electrophoresis.SettingA 950-bed teaching hospital in Seville, Spain.PatientsAll patients admitted to the hospital during the period from 1995 through 2008.MethodsThree successive interventions were studied: (1) contact precautions, with no active surveillance for MRSA; (2) targeted active surveillance for MRSA in patients and healthcare workers in specific wards, prioritized according to clinical epidemiology data; and (3) targeted active surveillance for MRSA in patients admitted from other medical centers.ResultsNeither the preintervention rate of MRSA colonization or infection (0.56 cases per 1,000 patient-days [95% confidence interval {CI}, 0.49-0.62 cases per 1,000 patient-days]) nor the slope for the rate of MRSA colonization or infection changed significantly after the first intervention. The rate decreased significantly to 0.28 cases per 1,000 patient-days (95% CI, 0.17-0.40 cases per 1,000 patient-days) after the second intervention and to 0.07 cases per 1,000 patient-days (95% CI, 0.06-0.08 cases per 1,000 patient-days) after the third intervention, and the rate remained at a similar level for 8 years. The MRSA bacteremia rate decreased by 80%, whereas the rate of bacteremia due to methicillin-susceptible S. aureus did not change. Eighty-three percent of the MRSA isolates identified were clonally related. All MRSA isolates obtained from healthcare workers were clonally related to those recovered from patients who were in their care.ConclusionOur data indicate that long-term control of endemic MRSA is feasible in tertiary care centers. The use of targeted active surveillance for MRSA in patients and healthcare workers in specific wards (identified by means of analysis of clinical epidemiology data) and the use of decolonization were key to the success of the program.

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