Observations of endotoxin-like activity associated with the Legionnaires' disease bacterium

Suspensions of Legionnaires' disease bacterium stored in sterilized tap water 279–287 days produced gelation ofLimulus amebocyte lysate. A 1-ml suspension of washed cells containing 109 viable organisms had aLimulus amebocyte lysate activity equivalent to 4 mg of endotoxin. This activity remained stable in samples that had been autoclaved at 121°C for 15 min. Both the autoclaved cells and filtrate of autoclaved cells were pyrogenic in inoculated rabbits. The Legionnaires' disease bacterium produces a substance or substances that have biological properties associated with endotoxin of more typical Gram-negative bacteria.