This invention relates to a method of treating infection by methicillin-nonsusceptibale bacteria, vancomycin-nonsusceptibale bacteria, penicillin-nonsusceptibale bacteria, clarithromycin-nonsusceptibale bacteria, or metronidazole-nonsusceptibale bacteria by administering to a subject in need thereof an effective amount of a quinolone compound of the formula shown in the specification.
