Molecular Characteristics and In Vitro Susceptibility to Antimicrobial Agents, Including the Des-Fluoro(6) Quinolone DX-619, of Panton-Valentine Leucocidin-Positive Methicillin-Resistant Staphylococcus aureus Isolates from the Community and Hospitals

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Abstract
Highly virulent, community-acquired methicillin-resistant Staphylococcus aureus (MRSA) strains with Panton-Valentine leucocidin (PVL) genes have been found increasingly worldwide. Among a total of 2,101 MRSA strains isolated from patients in hospitals in Japan, two were positive for PVL genes. One strain was identified as a community-acquired MRSA strain with genotype sequence type 30 (ST30) and spa (staphylococcal protein A gene) type 19 from Japan and was resistant only to β-lactam antimicrobial agents. The other strain was closely related to PVL + multidrug-resistant, hospital-acquired MRSA strains (ST30, spa type 43) derived from nosocomial outbreaks in the 1980s to 1990s in Japan but with a divergent sequence type, ST765 (a single-locus variant of ST30). Twenty-two PVL + MRSA strains, including those from Japan and those from other countries with various sequence types (ST1, ST8, ST30, ST59, and ST80) and genotypes, were examined for susceptibility to 31 antimicrobial agents. Among the agents, DX-619, a des-fluoro(6) quinolone, showed the greatest activity, followed by rifampin and sitafloxacin, a fluoroquinolone. The data suggest that DX-619 exhibits a superior activity against PVL + MRSA strains with various virulence genetic traits from the community as well as from hospitals.