and Activity of Omadacycline against Two Biothreat Pathogens, Bacillus anthracis and Yersinia pestis.

The activity and efficacy of omadacycline (OMC) were evaluated against the causative pathogens of anthrax and plague, and , respectively. MICs of OMC were determined by broth microdilution according to CLSI guidelines for 30 isolates each of and The efficacy of omadacycline was studied at a range of dosages in both a postexposure prophylaxis (PEP) murine model of anthrax and plague as well as in a delayed treatment model of inhalational anthrax. Omadacycline was active against (MIC of 1 μg/ml) and (MIC of 0.06 μg/ml). Omadacycline was less active than ciprofloxacin (CIP) against (CIP MIC of 0.03 μg/ml) but was more potent against (CIP MIC of 0.12 μg/ml). In the mouse model of infection, the survival curves for all treatment cohorts differed significantly from the vehicle control ( = 0.004). The median survival for the vehicle-treated controls was 6 days postchallenge, while all antibiotic-treated mice survived the entire study. Omadacycline treatment with 5, 10, or 20 mg/kg of body weight twice daily for 14 days had significant efficacy over the vehicle control in the treatment of aerosolized Additionally, for postexposure prophylaxis treatment of mice infected with , the survival curves for omadacycline (40 mg/kg twice daily), ciprofloxacin, and doxycycline cohorts differed significantly from the vehicle control ( < 0.0001). Omadacycline is potent and demonstrates efficacy against both and The well-characterized oral and intravenous pharmacokinetics, safety, and tolerability warrant further assessment of the potential utility of omadacycline in combating these serious biothreat organisms.