How does endotoxin trigger inflammation in otitis media with effusion

Objectives The relationship among microorganisms, endotoxin, and inflammatory mediators in otitis media with effusion (OME) was examined. Study Design Analysis of 152 middle ear effusions aspirated at the time of ventilation tube insertion from children with OME. Methods Effusion samples were cultured for pathogenic bacteria. The two primary cytokines, interleukin-1β (IL1β) and tumor necrosis factor (TNFα), and the adhesion molecules, intercellular and vascular adhesion molecule (ICAM-1 and VCAM-1), were quantified using the enzyme-linked immunosorbent assay (ELISA) technique. Endotoxin concentration was measured with a limulus amebocyte lysate assay, and total protein concentration was quantified using the Biorad microassay. Results The cultures of pathogenic bacteria were positive in 33 of the 152 effusions (22%), which contained more endotoxin and more of the primary cytokines than the 119 culture-negative effusions. Endotoxin and the primary cytokines were positively correlated, both in the whole material and in the sterile effusions alone. The adhesion molecules were positively correlated with each other, but not with endotoxin or the primary cytokines. Conclusions We found a positive correlation between endotoxin and the primary cytokines TNFα and IL1β in culture-positive OME effusions as well as in culture-negative ones, suggesting endotoxin-induced local production of TNFα and IL1β in the middle ear. ICAM-1 and VCAM-1 were also present in the middle ear, but their concentrations were not directly correlated to endotoxin or the primary cytokines.