Comparative antimycobacterial activities of ofloxacin, ciprofloxacin and grepafloxacin

Infections caused by non-tuberculous mycobacteria and multidrug-resistant M ycobacterium tuberculosis are difficult to treat. New compounds potentially active against these bacteria are therefore constantly being sought. Among them is grepafloxacin, a new C5 fluoroquinolone, A panel of 130 isolates o f mycobacteria including 33 M. tuberculosis isolates and 97 isolates of dif ferent species of atypical mycobacteria were analysed for susceptibility to grepafloxacin, ofloxacin and ciprofloxacin. The MICs of these fluoroquinol ones were determined using the agar-dilution method. Different mycobacteria l species showed different degrees of susceptibility to grepafloxacin, oflo xacin and ciprofloxacin but little difference was observed between the MICs of the three antibiotics against strains of the same mycobacterial species . In addition, to evaluate the intracellular activity of these drugs, six s trains of mycobacteria were studied using a human-macrophage infection mode l. Preliminary results of macrophage experiments showed that grepafloxacin was more active than ofloxacin and ciprofloxacin, particularly against Myco bacterium kansasii and, to a lesser degree, against Mycobacterium avium com plex and Mycobacterium marinum. However, the three fluoroquinolones had com parable activities against M. tuberculosis.