Novel Characteristics of Community-Acquired Methicillin-Resistant Staphylococcus aureus Strains Belonging to Multilocus Sequence Type 59 in Taiwan

Abstract

Community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) strains, which often produce Panton-Valentine leucocidin (PVL), are increasingly noted worldwide. In this study, we examined 42 MRSA strains (25 PVL-positive [PVL ⁺ ] strains and 17 PVL-negative [PVL ⁻ ] strains) isolated in Taiwan for their molecular characteristics. The PVL ⁺ MRSA strains included CA-MRSA strains with multilocus sequence type (ST) 59 (major PVL ⁺ MRSA in Taiwan), its variants, and worldwide CA-MRSA ST30 strains. The PVL ⁻ MRSA strains included the pandemic Hungarian MRSA ST239 strain, the Hungarian MRSA ST239 variant, MRSA ST59 (largely hospital-acquired MRSA strains) and its variants, the pandemic New York/Japan MRSA ST5 strain (Japanese type), and the MRSA ST8 strain. The major PVL ⁺ CA-MRSA ST59 strain possessed a tetracycline resistance-conferring ( tetK positive) penicillinase plasmid and a drug resistance gene cluster (a possible composite transposon) for multidrug resistance. Moreover, it carried a novel staphylococcal cassette chromosome mec (SCC mec ) with two distinct ccrC genes ( ccrC2 - C8 ). This SCC mec (previously named SCC mec type V _T ) was tentatively designated SCC mec type VII. Sequencing of the PVL genes revealed the polymorphisms, and the PVL ⁺ CA-MRSA ST59 strain possessed the ST59-specific PVL gene sequence. The data suggest that a significant amount of clonal spread is occurring in Taiwan and that the major PVL ⁺ CA-MRSA ST59 _Taiwan strain exhibits unique genetic characteristics, such as a novel SCC mec type and an ST59-specific PVL gene sequence.