Endotoxin in middle-ear effusions from patients with chronic otitis media with effusion.

Endotoxin concentrations were determined in middle-ear effusions (MEEs) from 89 children with chronic otitis media by using the Limulu's amoebocyte lysate assay. Mean concentrations of endotoxin in Haemophilus influenzae-positive and Streptococcus pneumoniae-positive MEEs were 157 and 21.8 ng/ml, respectively, and were significantly different (P less than 0.01). Endotoxin was also found in Gram stain-positive, culture-negative and Gram stain-negative, culture-negative MEEs, but the levels were not significantly different (P greater than 0.05). However, the endotoxin concentrations in both groups of culture-negative MEEs significantly lower than those found in MEEs that grew either H. influenzae or S. pneumoniae (P less than 0.05). These results show that endotoxin is present in a high percentage of human MEEs, including those that are culture negative, and may contribute to the pathogenesis of otitis media with effusion.