Compositions, formulae, devices and methods for the detection of target microorganisms, such as by visual immunoprecipitate assay, enzyme linked immunoassay, chemiluminescence, immunoblotting, or similar detection technology, wherein detection requires the discrimination among closely related genera, species and strains of antigenically related microorganisms based on immunological reactivity of a highly conserved antigen epitopes with a reagent system comprised of an antibody linked to a detecting reagent. The invention permits a detectable event to occur by exposing inaccessible but highly conserved and specific antigen epitopes to the detecting reagent. Exposure of such antigen epitopes without inactivating microbial metabolism allows for specific detection.