Detection of Endotoxin in the Blood of Patients with Sepsis Due to Gram-Negative Bacteria

A test for endotoxin was performed on the blood of 98 patients in whom septicemia due to gram-negative bacteria was suspected. The method was derived from a previous observation that endotoxin causes gelation of lysates of Limulus polyphemus amebocytes in vitro. Seventeen per cent of the patients studied had endotoxemia, as defined by this test. There was a good correlation between positive tests for endotoxin and bacteremia due to gram-negative organisms. Patients with pneumococcal pneumonia and bacteremia due to gram-positive organisms had negative tests. Endotoxin or endotoxin-like material was detected in the blood in concentrations from approximately 0.005 to 0.0005 μg per milliliter. Our data indicate that the limulus test is a sensitive, reliable and practical method for the detection of endotoxemia.