Abstract: A method is described for the detection, either qualitatively or quantitatively, of gastrointestinal microorganisms in samples, preferably fecal samples, using immunoassays, preferably electrochemiluminescence (ECL) immunoassays. The methods involve detection without the conventional processing steps typically required for such detection (e.g., lysing, enrichment, separation, or purification). The method comprises dilution of the sample thought to contain a specific microorganism, inactivation (e.g., heat inactivation) of the diluted sample, removal of solids from the inactivated diluted sample, and detection of the pathogen in the inactivated diluted sample, by conducting an electrochemiluminescence assay for a bound complex of antibody and antigenic derivative, thereby detecting and/or presumptively identifying the microorganism in the sample.