Antimicrobial effect on rabbit sinusitis after temporary ostial occlusion

A key precipitating factor in the pathogenesis of acute bacterial sinusitis (ABS) is ostiomeatal obstruction. It has been postulated that ABS cannot resolve until the sinus ostium is patent. The primary purpose of this study is to quantify sinusitis resolution after temporary ostial occlusion in a rabbit model. A secondary aim is to quantify bacterial clearance with and without antimicrobial therapy in Staphylococcus aureus infected sinuses. A blinded, placebo controlled study in 10 New Zealand white rabbits was performed using Merocel(R) as a temporary maxillary sinus ostial obstruction. Computerized tomography (CT) of the maxillary sinuses was obtained before and after bilateral ostial occlusion; sinuses were cultured and then the left sinus was injected with approximately 10(8) cfu/mL S. aureus. CT imaging and sinus cultures were obtained and then the ostial plugs were removed. Serial CT and cultures were done until sinusitis resolved and cultures were negative for S. aureus. Mean CT sinusitis scores increased with ostial obstruction and decreased with ostial plug removal (P < 0.0001 and P < 0.001). Injection of S. aureus did not significantly change mean CT sinusitis scores despite being cultured from 45% of sinuses. Antimicrobial therapy was not significant in reducing mean CT scan sinusitis scores or positive cultures. Resolution of mucosal swelling is more dependent on relief of ostial obstruction rather than antimicrobial therapy in this rabbit model.