Prospective Surveillance of Community‐Onset and Healthcare‐Associated Methicillin‐Resistant Staphylococcus aureus Isolated from a University‐Affiliated Hospital in Japan

Abstract

We conducted a prospective comparative study of community‐onset (CO) and healthcare‐associated (HA) methicillin‐resistant Staphylococcus aureus (MRSA) strains between 2000 and 2001 at Tokyo Women's Medical University Hospital (1,500 beds) in Japan. Of the 172 consecutive MRSA isolates analyzed, 13 (8%) were categorized as CO‐MRSA. The mean age of patients with CO‐MRSA was significantly younger than that of patients with HA‐MRSA. Most CO‐MRSA strains were isolated from skin and more likely to be susceptible to erythromycin, clindamycin, tetracycline, levofloxacin, and spectinomycin compared to HA‐MRSA isolates. Pulsed‐field gel electrophoresis (PFGE) analysis, staphylococcal cassette chromosome mec (SCCmec) typing, and multi‐locus sequence typing (MLST) revealed that CO‐MRSA strains were divided into the following multi‐clones: 3 clone A: II: ST5 (PFGE type: SCCmec type: MLST sequence type); 1 L: II: ST5; 1 H: IV: ST1; 1 I: IV: ST81; 2 D: IV: ST8; 1 B: IV: ST89; 1 B: IV: ST379; and 3 B: IV: ST91. Of the 159 HA‐MRSA strains, 124 (78%) belonged to a single clone (PFGE clone A: SCCmec type II: tst and sec positive: coagulase type II: multi‐drug resistance). Four CO‐MRSA strains belonging to PFGE clone B: SCCmec type IV: MLST clonal complex 509 (ST89, 91, 379) had the exfoliative toxin B (etb) genes, but all CO‐MRSA and HA‐MRSA strains did not possess the Panton‐Valentine leukocidin (pvl) genes. These results demonstrate that multiple lineages of CO‐MRSA have the potential for dissemination in the community in Japan.