Lipid A is a covalently bound lipid component of the gram-negative bacterial lipopolysaccharide, and represents the biologically active component in endotoxins. For the detection and quantification of lipid A in middle ear effusion (MEE) from patients with otitis media with effusion (OME), we raised antisera against lipid A in mice by repeated immunization with the conjugates with lipid A of Salmonella minnesota Re595 and bovine serum albumin, and developed an competitive enzyme-linked immunosorbent assay (ELISA) specific for lipid A. In the ELISA, 10 out of 15 samples from serous type of MEE (13.57±2.17 μg/ml, mean±SE), and 5 out of 6 from mucoid type of MEE (17.73±4.34 μg/ml, mean±SE) were positive. Lipid A present in MEE may contribute to the pathogenesis of both types of human OME.
