Evaluation of higher oral doses of cethromycin in a pneumonic rat model of infection and subsequent protection from 2 Y. pestis rechallenges. Groups of rats were exposed to a 30 LD50 of Y. pestis CO92 and administered cethromycin (Cethro) at the indicated doses. As a negative control, rats were administered PBS instead of cethromycin, while as a positive control, rats received 20 mg/kg/day of levofloxacin (Levo) orally. Drug treatments were administered for 6, 10, or 14 days, and administration lengths are indicated by different colored bars. Survivors were rechallenged twice following the first Y. pestis infection. As toxicity controls, uninfected rats were administered either 120 mg/kg or 140 mg/kg/day for 14 days. P values indicate statistical significance.