In vitro potency of moxifloxacin, clinafloxacin and sitafloxacin against 248 genetically defined clinical isolates of Staphylococcus aureus.

The in vitro potency of three newer fluoroquinolones, moxifloxacin, clinafloxacin and sitafloxacin was tested against 248 genetically defined Staphylococcus aureus isolates, comprising 116 unrelated S. aureus, seven heterogeneous intermediate vancomycin-resistant S. aureus strains as well as 125 clonally related methicillin-resistant S. aureus. All strains were susceptible to clinafloxacin and sitafloxacin based on an investigational breakpoint of 1 mg/L and were less influenced by mutations within the grl and gyr gene loci. In one-quarter to one-third of the strains tested, reserpine decreased slightly the MICs of moxifloxacin, clinafloxacin and sitafloxacin. Compared with moxifloxacin, clinafloxacin and sitafloxacin showed a significantly increased anti-staphylococcal potency.