Chlamydia trachomatis produces small amounts of an
endotoxin-like material. The Limulus
amoebocyte lysate assay was used to evaluate chlamydial cell cultures and also the exudates from adult male patients with non-gonococcal
urethritis, as a possible method to subdivide this condition into chlamydial and nonchlamydial
urethritis. In vitro
endotoxin assays were conducted in McCoy cell media using the Limulus assay, and
endotoxin levels were consistently 10-fold less at 24 h than at 0, 48, 72, and 96 h, which may be accounted for by the unique growth cycle of chlamydia. In 75 males with non-gonococcal
urethritis, urethral exudates were collected, serially diluted and assayed for
endotoxin content. Of these, 27 (36%) had positive chlamydial cultures and 48 were negative. There was no statistically significant correlation between the level of
endotoxin present and a positive or a negative culture for C. trachomatis (P greater than 0.05). Sensitivity and specificity of the assay were only 59% and 56%, respectively, at a 1 in 8 dilution; it was not useful in predicting chlamydial culture results in male patients with non-gonococcal
urethritis.