Experimental otitis media with effusion induced by lipopolysaccharide from Klebsiella pneumoniae. Mucociliary pathology of the eustachian tube.

Otitis media with effusion (OME) is generally benign and self-limiting but is often recurrent and can change into a chronic type. We have previously reported that intratympanic inoculation of lipopolysaccharide (LPS) from Klebsiella pneumoniae can develop experimental OME in the guinea pig. However, OME induced by 10 micrograms/ml of LPS was of a self-limiting type. Our hypothesis was that a higher concentration of LPS might develop a chronic OME because LPS reduces the ciliary activity in the tubotympanum in a dose related manner. In our present study we inoculated 100 micrograms/ml of LPS from K. pneumoniae into the tympanic cavity of the guinea pig, in the hope of illuminating a possible mechanism predisposing to the chronicity of the disease. A longer-term OME was observed after tympanic inoculation of 100 micrograms/ml of LPS. Ciliary activity in the Eustachian tube was depressed for a longer term by this dose than by the previous one. In addition to mucociliary pathologies and general inflammatory changes similar to those induced by 10 micrograms/ml of LPS, intracytoplasmic ciliary cysts were observed after inoculation of 100 micrograms/ml of LPS, which appeared to show disturbed ciliogenesis and chronic mucociliary lesions. In conclusion, intratympanic inoculation of a higher concentration of LPS developed a longer-term OME in the guinea pig, which was supported by functional as well as morphological examinations.