EFFICACY OF CLARITHROMYCIN TREATMENT OF ACUTE OTITIS-MEDIA CAUSED BY INFECTION WITH PENICILLIN-SUSCEPTIBLE, PENICILLIN-INTERMEDIATE, AND PENICILLIN-RESISTANT STREPTOCOCCUS-PNEUMONIAE IN THE CHINCHILLA

Because of the increasing frequencies of recovery of penicillin-resist ant Streptococcus pneumoniae from the middle ears of children with acu te otitis media, non-beta-lactam antibiotics are being explored as tre atment alternatives to amoxicillin. In this study, the efficacy of a 1 0-day course of clarithromycin was evaluated with chinchillas. After t he pharmacokinetic profiles for clarithromycin were established, 180 a nimals were assigned to one of three susceptibility groups (n = 60/gro up; penicillin-susceptible, -intermediate, and -resistant S. pneumonia e), and the right middle ear was infected with the appropriate strain of S. pneumoniae. Equal numbers of animals in each group were treated orally beginning on day 2 with a 10-day course of clarithromycin (15 m g/kg of body weight; given twice a day) or amoxicillin as a control (2 0 mg/kg twice a day), On days 4, 9, and 13, otomicroscopy and tympanom etry were performed, and on day 13, the middle ears were cultured for bacteria, The results showed 100% eradication of the challenge organis m in both treatment groups for the susceptible strains of S. pneumonia e. Cultures were negative in 87 and 74% (P > 0.05) of the animals chal lenged with the intermediate resistant strains and in 100 and 56% (P < 0.05) of the animals challenged with the resistant strains and treate d with clarithromycin and amoxicillin, respectively, There were no dif ferences between treatments in the diagnosis of effusion for any group , These results support the use of the chinchilla to evaluate drug eff icacy in the treatment of acute otitis media and show clarithromycin t o be effective in sterilizing the middle ears of animals challenged wi th penicillin-susceptible, -intermediate, and -resistant strains of S. pneumoniae.