Experimental acute sinusitis in rabbits. A bacteriological and histological study.

A bacteriological and histological study of experimentally induced acute pneumococcal sinusitis was performed in 69 New Zealand White rabbits. The sinus ostium was blocked on one side on the first day of the experiment. On the second day, 10(7)-10(9) Streptococcus pneumoniae in 1 ml were injected into the same sinus cavity. Purulent sinusitis developed unilaterally in all rabbits. Histological examination of the sinus mucosa revealed edema, dilated venules, leukocytic infiltration of the mucosa as well as localized epithelial lesions. On staining with acridine orange at pH 4.0, the bacteria were observed in the secretion but not in the mucosa. When we used Streptococcus pneumoniae subjected to an animal passage, the bacteria were re-isolated in 9/10 infected sinuses. Neither sole occlusion of the ostium nor injection of pneumococci into a sinus cavity with a patent ostium resulted in a bacterial sinusitis. Obstruction of the sinus ostium and the use of a virulent Streptococcus pneumoniae strain were essential for the induction of sinusitis in rabbits.