Studies in plaque pathogenicity: II. A technique for the specific detection of endotoxin in plaque samples using the limulus lysate assay

The purpose of this study was to define a technique for the positive identification of endotoxin in heterogenous dental plaque samples. An extraction technique, which includesan acotone wash and trichloroacetic acid precipitation followed by pphenol‐water extraction was developed to reduce the level of both proteins and nucleic acids in individual plaque samples. Ten subgingival samples of adherent and loosely adherent treated in this manner retained limulus lysate almost exclusively in the phenol phase; ten supragingival samples retained activity in the phenol and water phases. further treatment of all of these samples with ribonuclease A and T₁ and with lysozyme did not alter assay results, suggesting that the limulus lysate activity detected was due to Gram‐negative Bacterial cell wall fractions. this technique may be useful in determining endotoxin activity in plaque samples and ultimately, in evaluation the effectiveness of chemotherapeutic agents in reduction of plaque endotoxin.