Postantibiotic effect and postantibiotic sub-MIC effect of levofloxacin compared to those of ofloxacin, ciprofloxacin, erythromycin, azithromycin, and clarithromycin against 20 pneumococci.

The postantibiotic effect (PAE) (10 times the MIC of quinolones, 5 times the MIC of macrolides) and postantibiotic sub-MIC effect (PAE-SME) at 0.125, 0.25, and 0.5 times the MIC were determined for levofloxacin, ciprofloxacin, ofloxacin, erythromycin, azithromycin, and clarithromycin against 20 pneumococci. Quinolone PAEs ranged between 0.5 and 6.5 h, and macrolide PAEs ranged between 1 and 6 h. Measurable PAE-SMEs (in hours) at the three concentrations were 1 to 5, 1 to 8, and 1 to 8, respectively, for quinolones and 1 to 8, 1 to 8, and 1 to 6, respectively, for macrolides.