Consequences of delayed ciprofloxacin and doxycycline treatment regimens against Francisella tularensis airway infection.

This study examines the efficacy, bacterial load, and humoral response of extensively delayed ciprofloxacin or doxycycline treatments following airway exposure of mice to Francisella tularensis subsp. holarctica (strain LVS) or to the highly virulent F. tularensis subsp. tularensis (strain SchuS4). A delay in onset of both antibiotic treatments allowed the rescue of all LVS-infected animals. However, for animals infected with SchuS4, only ciprofloxacin was efficacious and prolongation of treatment rescued all animals.