Limulus lysate positivity and Herxheimer-like reactions in leptospirosis: a placebo-controlled study.

Jarisch-Herxheimer reactions are characteristic of some spirochetal diseases and have been reported in leptospirosis, but their pathogenesis and relationship to endotoxin remain unclear. Serial limulus amebocyte lysate assays (LAL) for endotoxin were performed on 40 patients with proven leptospirosis who were monitored for reactions after receiving either intravenous penicillin (24) or saline placebo (16). No Herxheimer-like reactions were observed, although 78% of patients had at least one positive LAL. Serum creatinine, serum bilirubin, and white blood cell counts were significantly higher (P less than .01) in simultaneously drawn LAL-positive specimens than in negative ones. Delayed hepatic clearance of endotoxin due to liver dysfunction may explain the high LAL positivity rate, since assay results correlated with severity of disease but not with the presence or absence of spirochetes. Fear of a Herxheimer-like reaction should not dissuade clinicians from administering antibiotics to patients with leptospirosis.