Serum bactericidal activity of the methoxyfluoroquinolones gatifloxacin and moxifloxacin against clinical isolates of Staphylococcus species: are the susceptibility breakpoints too high?
Healthy volunteers received a single dose of gatifloxacin and moxifloxacin (400 mg each), and serum samples were obtained from these volunteers over a 24-h period. Prolonged (> or =12 h) serum bactericidal activity (SBA) was observed for both agents against staphylococcal isolates with minimum inhibitory concentrations (MICs) of gatifloxacin of < or =0.5 mug/mL. In strains with gatifloxacin MICs of 1.0 mug/mL, SBA was observed for < or =6 h, and, for isolates with gatifloxacin MICs of 2.0 mug/mL, little or no SBA was observed for either drug. The relative lack of SBA against less susceptible strains of staphylococci suggests that the current susceptibility breakpoint concentration (MIC, 2.0 mug/mL) for these methoxyfluoroquinolones against Staphylococcus is too high.
Department of Medicine and Pharmacology, Michigan State University, East Lansing, Michigan 48824, USA. steing@msu.edu
Gary E
GE
Stein
Sharon
S
Schooley
Glenn W
GW
Kaatz
D000328:Adult; D001372:Aza Compounds / Q000097:blood / Q000494:pharmacology*; D001770:Blood Bactericidal Activity; D024901:Drug Resistance, Multiple, Bacterial; D024841:Fluoroquinolones / Q000097:blood / Q000494:pharmacology*; D000077734:Gatifloxacin; D006801:Humans; D008297:Male; D008826:Microbial Sensitivity Tests; D008875:Middle Aged; D000077266:Moxifloxacin; D011804:Quinolines / Q000097:blood / Q000494:pharmacology*; D015610:Serum Bactericidal Test; D013210:Staphylococcus / Q000187:drug effects*
D001372:Aza Compounds; D024841:Fluoroquinolones; D011804:Quinolines; D000077734:Gatifloxacin; D000077266:Moxifloxacin