Prevalence of methicillin-resistant Staphylococcus aureus based on culture and PCR in inpatients at a tertiary care center in Tokyo, Japan

We investigated active screening for colonization with methicillin-resistant Staphylococcus aureus (MRSA) on admission and weekly follow-up surveillance after admission to a tertiary care center (TCC) between June 2007 and 31 December 2007. Eleven percent (30/267) of patients were found to be positive for MRSA by polymerase chain reaction (PCR) and/or culture on admission; 5% (12/267) became positive during the TCC stay. The major primary diagnoses in MRSA-positive patients were pneumonia and cerebrovascular diseases. Twenty-two (52%) of 42 patients were found to be MRSA positive by both PCR and culture, compared with 19 (45%) of 42 who were PCR positive and culture negative. These findings suggest that active surveillance with PCR is highly sensitive and useful for the detection of MRSA colonization. To our knowledge, this is the first report of active surveillance of MRSA by PCR and bacterial culture in critically ill inpatients in Japan.