Comparison of telithromycin, a new ketolide, with erythromycin and clarithromycin for the treatment of Haemophilus influenzae pneumonia in suckling, middle aged and senescent mice.

We studied the efficacy of telithromycin in Haemophilus influenzae pneumoniae in three different age groups of mice. Pneumonia was produced by endotracheal instillation of 1 x 10(4) CFU/ml of bacteria and treatment was initiated with saline for control and compared with two different doses, 50 and 100 mg/kg per BID telithromycin twice a day for 1 week. For comparison, we used erythromycin (ERY) and clarithromycin (CLA), both given twice a day at 50 mg/kg per BID. Some animals were euthanized on the third or 7th day of therapy and their lung tissue was cultured for bacteria. Presence of bacteria was considered a failure and a sterile lung was considered cured. As expected, about one half of middle-aged animals (8-10 months) were cured on saline. In contrast, almost none of the young (2-3 weeks) and old animals (18-20 months) were cured without antibiotic therapy. Among the young, the cure rates with telithromycin, ERY and CLA were 81, 50 and 33%, respectively. Of the senescent mice, the cure rate with ERY was 50% whereas the rates with CLA and telithromycin (50 mg/kg) were 62 and 75%, respectively. In conclusion, telithromycin is effective against H. influenzae at both extremes of life.