Universal immuno-stick test for direct rapid identification of microbial antigens within 5 minutes. Preliminary...

Based on experiences with ELISA and biochemical fluorescence assays we have developed a new serologic identification system for detecting all conceivable particle and soluble antigens within 5 min using a very simple, sensitive procedure. This assay represents a sandwich ELISA that has been modified with regard to the sorbent, the enzyme substrate and the identification step. The test is performed as follows: 10 microliter aliquots of antigen dilution, specific or control antibody, respectively, and a phosphatase-conjugated anti-antibody are consecutively mixed. A small strip of special indicator sorbent paper (test stick) is moistened with this mixture for one minute. Subsequently it is dipped 3-5 times alternately in 0.1 M NaOH and a solution of the enzyme-substrate 4-methylumbelliferyl phosphate and immediately evaluated under a UV lamp. Positive samples instantaneously show brilliant light blue fluorescence and decolorization from dark red to white. Although the principle behind the reaction is not yet fully understood, the test works specifically and sensitively within a pg range. Thus far, for example, we have been able to identify Salmonella from suspended milk powder and streptococci from milk (3-5 cells/ml) without previous incubation, enterotoxins from staphylococcal colonies, Aflatoxin M1 and organ-phosphates. Results from examinations of staphylococcal enterotoxins are presented in more detail. Moreover, using a defined antigen, antibodies from different sera could be identified in the same rapid, sensitive and specific manner. Thus, we are convinced that the usual time-consuming enrichment methods for isolating pathogenic bacteria and other immunogenic substances as also current serologic assays will turn out to be superfluous.