Effect of intranasal inoculation of Streptococcus pneumoniae on the structure of the surface carbohydrates of the chinchilla eustachian tube and middle ear mucosa

The changes in the cell surface carbohydrates of the eustachian tube (ET) and middle ear subsequent to the intranasal (i.n.) inoculation of Streptococcus pneumoniae (Spn) type 6A were studied in the chinchilla model of otitis media (OM) using a lectin histochemical technique with six different lectins (SNA, WGA, Succ WGA, BSL II, PNA, ECL). The labeling pattern revealed not only the removal of the terminal sialic acid, but also exposure of N-acetylglucosamine (GlcNAc), a component of the trisaccharide receptor for Spn previously identified on human pharyngeal cells. The removal of sialic acid residues progressed from the nasopharyngeal to the tympanic orifice and was most Pronounced in those animals from which Spn could be isolated from the middle ear. Our data indicate an alteration of the normal lectin labeling pattern and exposure of GlcNAc restricted mainly to the roof and neck portion, along the course of the eustachian tube. Exposure of part or all of a Spn adherence receptor structure by the pneumococcal enzymes, may facilitate colonization, invasion of the middle ear, and induction of OM.