Systems of competitive immunofluorometric assay of Salmonella enterica bacteria, comprising conjugates of antibodies with europium chelate

Bioanalytical systems specific to Salmonella enterica bacteria have been developed and studied. The systems are based on the immunochemical binding of lipopolysaccharide (LPS) antigens of these pathogenic microorganisms to mono- and polyclonal antibodies conjugated with a europium chelate. The quantitative determination of the cells was carried out in immunoassay systems by measuring the Eu³⁺ time-resolved fluorescence (dissociation-enhanced lanthanide fluorescence immunoassay, DELFIA) systems. In the DELFIA microplate system, comprising labeled polyclonal antibodies in solution and a LPS-protein conjugate on the solid-phase, the following analytical parameters were achieved: cell concentration measurement range – from 10⁴ to 10⁷ CFU/ml, sensitivity (IC₅₀) – 3 · 10⁵ CFU/ml, the limit of detection (IC₁₀) – 1.5 · 10⁴ CFU/ml, and the coefficient of variation – from 4,5 to 8.0 %. The broad specificity of this system enabled to detect Salmonella enterica of various serotypes. The possibility of testing samples of culture medium and milk without prior dilution was demonstrated. The recovery rate of samples containing Salmonella enterica was found to be 88–110 %. The presented development can serve as the basis for a practical kit of reagents to monitor Salmonella enterica bacteria in food products.

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