Spread of the community-acquired methicillin-resistant Staphylococcus aureus USA300 clone among family members in Japan.

The USA300 clone is a highly-virulent community-acquired methicillin-resistant Staphylococcus aureus, which has been predominant in the United States. In a previous study, we isolated the USA300 clone from an 11-month-old Japanese girl, who lived in Saitama (Japan), and suffered from cellulitis and sepsis, and subsequently osteomyelitis, in 2008. In this study, we searched for the source of such USA300 infection in three related families (the patient's grandfather and grandmother, having a USA300-infected daughter [F2D], and a mother [F3M] who was a sister of F2D's mother). In January, 2008, F3M and her family members visited Hawaii and were treated in a hospital for gastroenteritis (with diarrhea) with an intravenous drip for F3M. After their return to Japan in January, F3M suffered from unusually frequent (more than 10 times) skin soft-tissue infections (SSTIs) until successful chemotherapy in July in Saitama. In the same summer season, SSTI was observed in 7 of 11 family members (63.6%). This dense spread of SSTI was followed by cellulitis and sepsis (USA300-isolated case) in October and subsequent osteomyelitis in December in F2D. After successful chemotherapy for the patient (F2D), no new SSTI cases were observed among the family members, and no USA300 colonization was observed when examined in December, 2009. The data suggest the first spread of the USA300 clone in Japan with related families at the core and that such USA300 spread in the community is likely to have occurred in the summer season in Japan.