Serum Bactericidal Activity of the Methoxyfluoroquinolones Gatifloxacin and Moxifloxacin against Clinical Isolates of Staphylococcus Species: Are the Susceptibility Breakpoints Too High?

• Published in: Clinical infectious diseases 2003-11, Vol.37 (10), p.1392-1395
• Main Authors: Stein, Gary E., Schooley, Sharon, Kaatz, Glenn W.
• Format: Article
• Language: English
• Subjects: Adult; Antibacterial agents; Antibacterials; Antibiotics. Antiinfectious agents. Antiparasitic agents; Aza Compounds - blood; Aza Compounds - pharmacology; Bacterial diseases; Biological and medical sciences; Blood Bactericidal Activity; Brief Reports; Dosage; Drug design; Drug Resistance, Multiple, Bacterial; Fluoroquinolones; Fluoroquinolones - blood; Fluoroquinolones - pharmacology; Human bacterial diseases; Humans; Infections; Infectious diseases; Male; Medical sciences; Microbial Sensitivity Tests; Middle Aged; Pharmacology. Drug treatments; Quinolines - blood; Quinolines - pharmacology; Research studies; Serum Bactericidal Test; Staphylococcal infections, streptococcal infections, pneumococcal infections; Staphylococcus; Staphylococcus - drug effects; Staphylococcus aureus; Volunteerism
• ISSN: 1058-4838; 1537-6591
• DOI: 10.1086/379518

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 (⩾12 h) serum bactericidal activity (SBA) was observed for both agents against staphylococcal isolates with minimum inhibitory concentrations (MICs) of gatifloxacin of ⩽0.5 µg/mL. In strains with gatifloxacin MICs of 1.0 µg/mL, SBA was observed for ⩽6 h, and, for isolates with gatifloxacin MICs of 2.0 µg/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 µg/mL) for these methoxyfluoroquinolones against Staphylococcus is too high.