The bactericidal activity of levofloxacin compared with ofloxacin, D-ofloxacin, ciprofloxacin, sparfloxacin and cefotaxime against Streptococcus pneumoniae.

The bactericidal activity of levofloxacin was compared with that of four other quinolones and one cephalosporin against four strains of Streptococcus pneumoniae with varying degrees of penicillin G susceptibility. Levofloxacin was found to be the most bactericidal quinolone at its optimum bactericidal concentration, followed by ofloxacin, ciprofloxacin, sparfloxacin and D-ofloxacin, in that order. There was no correlation between quinolone-susceptibility and penicillin-susceptibility with any quinolone tested. To allow a comparison between the bactericidal activity of the quinolones and cefotaxime to be made a bactericidal index was used. Against two penicillin-sensitive pneumococci and a penicillin-intermediate pneumococcus, cefotaxime was the most potent antibacterial agent tested, followed by levofloxacin. However, against the penicillin-resistant pneumococcus, levofloxacin was considerably more potent than cefotaxime. The remaining quinolones tested were inferior to levofloxacin. Levofloxacin has enhanced activity against pneumococci compared with clinically available quinolones. In addition, levofloxacin may be the future quinolone of choice in the treatment of penicillin-resistant pneumococci.