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 Limulus 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 < 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 > 0.05). However, the endotoxin concentrations in both groups of culture-negative MEEs were significantly lower than those found in MEEs that grew either H. influenzae or S. pneumoniae (P < 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.