Disclosed herein are methods of treating a pulmonary bacterial infectioncomprising bacteria growing under anaer-obicconditions using a fluoroquinolone antibiotic. The fluoroquinolone antibioticmay, for example, be levofloxacin or ofloxacin.Also disclosed are methods of inhibiting bacteria growing under anaerobicconditions by exposing the bacteria to an amount offluoroquinolone antibiotic effective to inhibit growth of said bacteria.