Reversed passive latex agglutination tests for the rapid and simple detection of bacterial toxins

Introduction A series of test kits for detecting bacterial toxins have recently been put on the market byOXOId Limited. These kits employ reversed passIve tatex agglutination (RPLA) as the assay method and, in this article. the development, characteristics and value of the method for detecting bacterial toxins are briefly reviewed . Bacteria produce enzymes and toxins With vanous biological activities. Some of the products of their metabohsm such as toxins are closely associated With human diseases, sometimes acting as causative agents. It ;s tllerelore very useful to confirm the presence of tox ins in test samples for the diagnosis of certain diseases, However. If the assay to detect such toxins involves expensive equip· ment. technically difficult or lengthy procedures, experience has shown that the test will not be widely used in the diagnOSIs of disease. Various techniques have been dev· eloped for the detection of bacterial toxins. The easiest and most economical method which does not requi re specia l equipment IS that based upon the agglutination of preserved erythrocytes or latex particles as a reaction Indicator. RPLA was selected for the assay because of ItS excellenl sensitivity and specifiCity. It was originally developed as a method to detect staphylococcal enlerotoxln and later found sUitable for fun her applications In the detection of Vibno cho/erae enterotoxin. Esche(fCh18 colt heat-labile enterotoxin and Clostridium perfrmgens enter· otOXIn. In the following part of this article these applications 01 RPLA for enterotoxin detection are described. Salmon and Tew 1 first described RPLA as a method to detect staphylococcal enterotoxins. The sensitivity of their method in detecting staphylococcal enterotoxin B was 1 ng in 1 ml 01 sample, a remarkably high sensilivity at that time. However, the method remained widely unused because it could detect enterotoxin B only whilst five immunologically different enlerotoxins A to E were known to exist. The low specificity of the sensitized tatex prepared by ditutlng specific antl·enterotoxin sera according to their method was another serious drawback. The practical application of RPLA for detecting bactenat toxins had to walt untilihe pUrlflca· lion of antl ·enterotoxln serum became feasible by affinity chromatography uSing staphylococal enterotoxlns as ligands.