Effects of antibiotics and steroid on middle ear mucosa in rats with experimental acute otitis media

The prevention of mucosal changes induced by experimental pneumococcal otitis media by means of antibiotics has been demonstrated previously. However, the effect of combined antibiotic and steroid therapy on the middle ear mucosa in acute otitis media (AOM) has not been determined. The right middle ears of 27 rats were inoculated with a log-phase type 3 Streptococcus pneumoniae, with the left ears serving as controls. Penicillin G was administered to nine rats and penicillin G and dexamethasone in combination were administered to nine rats after bacterial challenge; the remaining nine rats were not treated. Three animals from each group were sacrificed on Days 4, 7 and 14 after challenge. Tympanic membranes and middle ear mucosa were examined using otomicroscopy and light microscopy. Structural changes were diminished in both the antibiotic-treated and antibiotic + steroid-treated groups, compared with those in the untreated infected controls. The antibiotic + steroid-treated group showed the most marked decrease in structural change, especially in the mucosal metaplasia to the secretory epithelium. The results suggest that combination therapy with antibiotics and steroid in AOM is the most effective at reducing the treatment period and preventing persistent mucosal changes, which may decrease the risk of development of secretory otitis media as a sequela of AOM.