One-step rapid immunochromatographic method for detection of diphtheria toxin in different water samples (phosphate buffer, milk, human nasopharyngeal swab) with the conjugate of monoclonal antibodies labeled with colloidal gold was developed. The limit of visible detection of the diphtheria toxin is 10 ng/ml and 15 min time analysis. The use of silver sensitivity enhancement and scanning equipment decreased the detection limit to 1.25 ng/ml.

Instrument free methods for detection of staphylococcal enterotoxin A (SEA) in samples of drinkable dairy products and meat broth using immunochromatography (IC) and dot assay were developed. A conjugate of monoclonal antibodies (MA) to SEA with colloid gold (CG) was used as the detecting com ponent in IC; the MA CG conjugate or biotinylated SEA antibodies and streptavidin peroxidase conjugate (STR HRP) were used for conducting the dot assay. The results of the SEA analysis with the developed method and with the immunoenzymatic assay (IEA) were compared. The limit of detection in ng/mL was: 10 (IC), 20 (dot analysis, MA CG), 10 (dot analysis, STR HRP), and 4 (IEA). The analysis time in min was: 25 (IC), 60 (dot assay, MA CG), 70 (dot assay, STR HRP), and 150 (IEA). The simplicity and availability of the developed instrumentless detection methods allow conducting single and mass testing in low resource laboratories as well as outside laboratories.

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