IN-VIVO EFFICACIES OF AMOXICILLIN AND CEFUROXIME AGAINST PENICILLIN-RESISTANT STREPTOCOCCUS-PNEUMONIAE IN A GERBIL MODEL OF ACUTE OTITIS-MEDIA

The comparative efficacies of amoxicillin and cefuroxime against acute otitis media caused by a penicillin-resistant (MIC, 2 mu g/ml) Strept ococcus pneumoniae strain were assessed in a gerbil model by challengi ng each ear with 10(7) bacteria through transbullar instillation. Each antibiotic was tested at two doses (5 and 20 mg/kg of body weight) ad ministered at 2, 10, and 18 h postinoculation, Samples were obtained f rom the middle ear (ME) on days 3 and 7 postinoculation for determinat ion of bacteria! counts. Only amoxicillin, at both doses, was able to significantly halt the weight loss in animals, reducing both the numbe r of culture-positive animals and the bacterial concentration in ME sa mples versus the values for untreated animals. Comparison of the effic acies between the antibiotics, determined by their ability to achieve culture-negative ME specimens, showed that amoxicillin at 5 mg/kg was significantly more active than cefuroxime at the same dose. The use of higher doses of either amoxicillin or cefuroxime did not produce sign ificantly better results than those obtained with the lower dose but c aused a greater inflammatory response. The more favorable results obta ined with amoxicillin compared with those obtained with cefuroxime cou ld be related to the antimicrobial susceptibility of the pneumococcal strain (MICs and minimum bactericidal concentrations of 1 and 1 mu g/m l and 4 and 4 mu g/ml for amoxicillin and cefuroxime, respectively) as well as to the better pharmacokinetic parameters obtained with amoxic illin.