Epidemiological and microbiological analysis of community-associated methicillin-resistant Staphylococcus aureus strains isolated from a Japanese hospital

Reports of community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) infections have recently increased in Japan; however, these studies contain limited information on their epidemiology. We performed a single-center study in the Tokyo Medical University Hospital located in Shinjuku, a central area of Tokyo, Japan. From 2,099 MRSA isolates obtained during July 2007 to March 2009, we selected 44 MRSA isolates with a MIC of <2 μg/mL for imipenem. Among 44 isolates, 28 strains had type IV or type V SCCmec, and we classified them as CA-MRSA. We identified only 1 Panton-Valentine leukocidin (PVL)-positive MRSA strain, which belonged to SCCmec type V. The PVL-positive CA-MRSA strain was isolated from a patient with multiple subcutaneous abscesses. The patient had returned to Japan from India; thus, the strain may have been contracted from outside of Japan. Thirteen (46.4%) and 15 strains (53.6%) were isolated from outpatients and inpatients, respectively. The major sites of infection included the respiratory tract (8 strains, 28.6%), skin/soft tissue (4 strains, 14.3%), and nasal cavity (4 strains, 14.3%). It is important to note that the most common site of CA-MRSA infection in inpatients was the respiratory tract; respiratory infections with CA-MRSA frequently cause severe infectious diseases.