Predominant Dissemination of PVL-Negative CC89 MRSA with SCCmecType II in Children with Impetigo in Japan

Background . The ratio of CA-MRSA in children with impetigo has been increasing in Japan. Methods . Antimicrobial susceptibilities of 136 S. aureus isolates from children with impetigo were studied. Furthermore, molecular epidemiological analysis and virulence gene analysis were performed. Results . Of the 136 S. aureus isolates, 122 (89.7%) were MSSA and 14 (10.3%) were MRSA. Of the 14 MRSA strains, 11 belonged to CC89 (ST89, ST91, and ST2117) and carried diverse types of SCC mec : type II (IIb: 3 strains; unknown subtype: 4 strains), type IVa (2 strains), and unknown type (2 strains). The remaining three strains exhibited CC8 (ST-8)-SCC mec type VIa, CC121 (ST121)-SCC mec type V, and CC5 (ST5)-nontypeable SCC mec element, respectively. None were lukS -PV- lukF -PV gene positive. Gentamicin- and clarithromycin-resistant strains were frequently found in both MRSA and MSSA. Conclusions . PVL-negative CC89-SCC mec type II strains are the most predominant strains among the CA-MRSA strains circulating in the community in Japan.