Role of Streptococcus pneumoniae and Haemophilus influenzae in the development of acute otitis media and otitis media with effusion in a gerbil model.

The efficacy of amoxicillin/clavulanate and cefuroxime was determined in a gerbil model of otitis media with a mixed Streptococcus pneumoniae plus Haemophilus influenzae middle ear (ME) infection. Results were compared with those obtained in a previous single H. influenzae model. All untreated animals inoculated with the mixed inoculum developed acute otitis media (AOM), whereas 86.7% of those inoculated with H. influenzae developed otitis media with effusion (OME). Antibiotics eradicated H. influenzae from the ME more efficiently in AOM than in OME, and this difference was highly significant (P</=.001) after administration of 5 mg/kg of either drug (amoxicillin/clavulanate, 100% vs. 10%; cefuroxime, 73.3% vs. 10%). Efficacy was predicted by the relation of in vitro susceptibility and ME antibiotic concentration, which was 2.7 times higher in AOM than in OME. In the mixed otitis model, the most efficacious antibiotic was able to prevent AOM, but >80% of animals developed culture-negative OME.