Determination of lipid A in human middle ear effusions with the competitive ELISA technique.

Lipid A is a covalently bound component of gram-negative bacterial lipopolysaccharides and is the biologically active component in endotoxin. In order to detect and quantitate lipid A in middle ear effusions (MEE) from patients with otitis media with effusion (OME), antisera against lipid A were produced in mice by repeated immunization with conjugates using lipid A from Salmonella minnesota Re595 and bovine serum albumin. As a result, a competitive enzyme-linked immunosorbent assay (ELISA) was developed that was specific for lipid A. From the ELISA results, 10 out of 15 samples from the serous type MEE (mean, 13.57 +/- 2.17 micrograms/ml) and 5 out of 6 from the mucoid type MEE (17.73 +/- 4.34 micrograms/ml) were positive. These findings indicate that lipid A may contribute to the pathogenesis of both types of human OME.