To determine if endotoxin liberation occurs after antibiotic administration to patients with syphilis, serial plasma samples were obtained from 15 patients receiving intramuscular penicillin G benzathine for secondary syphilis. The endotoxin content of these plasma samples was determined using a Limulus lysate assay (detection limit, 0.025 ng of reference Escherichia coli endotoxin per milliliter of patient plasma). Although secondary syphilis is the stage of syphilis having the greatest burden of spirochetes and the highest incidence of Jarisch-Herxheimer reactions, no endotoxin was detected in plasma either before or after antibiotic therapy. Despite the absence of detectable endotoxemia, five patients experienced mild Jarisch-Herxheimer—like reactions. These results suggest that endotoxin is not an important factor in either secondary syphilis or the reactions associated with antibiotic therapy of this disease.
Shenep JL, Feldman S, Thornton D. Evaluation for Endotoxemia in Patients Receiving Penicillin Therapy for Secondary Syphilis. JAMA. 1986;256(3):388-390. doi:10.1001/jama.1986.03380030090035