Clinical and pathogenic features of SCCmec type II and IV methicillin-resistant Staphylococcus aureus in Japan

Staphylococcal chromosomal cassette mec (SCCmec) type IV methicillin-resistant Staphylococcus aureus (MRSA) has rapidly disseminated in healthcare settings, and its characteristics in the United States and Europe are well known. Because Japanese SCCmec type IV MRSA clones are different and less well documented, this retrospective, single center study was done to determine and compare the characteristics of SCCmec type II and IV MRSA in Japan. For the analysis, 55 SCCmec type II and 101 type IV MRSA samples were collected from lower respiratory tract specimens or from skin or soft tissue. The patients of the SCCmec type IV group were significantly younger than those of the type II group (P < 0.001). The rate of MRSA pneumonia was significantly lower for SCCmec type IV than for type II (7.8% vs 29.0%, P = 0.026). In contrast, the rate of skin and soft tissue infection was not significantly different (66.0% vs 61.9%, P = 0.788). The distribution of MRSA pathogenic genes (sea, seb, sem, seo) was significantly different between SCCmec types II and IV (P < 0.001), which indicates that their clonal complex may be completely different. Interestingly, all SCCmec type II MRSA that caused MRSA pneumonia had seb and egc and lacked tst that belonged to sequence type (ST) 764. This is the first study to reveal and compare the characteristics of Japanese SCCmec type II and type IV MRSA. The information from this study will be helpful for the management of Japanese MRSA infection.