In vitro activity of E-4868, a new trifluoroquinolone, compared to six similar compounds

The compound E-4868 (Laboratorios Dr. Esteve) is a trifluoro, 7-azetidinyl quinolone with properties resembling those of other fluoroquinolones. Its activity in vitro was compared to that of six other similar drugs against more than 700 nosocomial isolates using standard methods. The MIC50s of E-4868 for enteric bacilli ranged from 0.015 to 0.25 micrograms/ml, being highest for Providencia spp. Pseudomonas aeruginosa strains were two-fold more susceptible to E-4868 than to ofloxacin. MICs of E-4868 for Haemophilus influenzae, Moraxella catarrhalis and pathogenic Neisseria spp. were all < or = 0.12 micrograms/ml. E-4868 was equal in activity to or eight-fold more active than ciprofloxacin against gram-positive cocci. The MICs of E-4868 for pneumococci were all < or = 0.5 micrograms/ml but anaerobes such as Bacteroides fragilis were generally less susceptible (MIC90, 4 micrograms/ml). There was almost complete cross-resistance to several other fluoroquinolones. Resistant mutants were selected by a multiple passage technique but the rate of mutation to resistance was very low (< 10(-8)) at an 8 x MIC.