Hemolytic
Disclosed herein is an immunoassay method for detecting the detection target antigen in an analyte through extraction with an extraction agent. The method is characterized in that the detection is performed in the presence of a cyclic oligosaccharide. The method is also characterized in the use of an immunochromatography kit for detecting gram-positive bacteria in an analyte, and that is configured from an analyte dilution solution, a sample dropping part, an antigen extracting part, a labeling substance retaining part, an immunochromatography medium having a detection part, and an absorption part, and in which an organic acid is retained in the antigen extracting part. The immunochromatography kit contains a cyclic oligosaccharide and a nitrite compound by containing at least one of a cyclic oligosaccharide, a nitrite compound, and a mixture thereof in the analyte dilution solution and/or the sample dropping part.
1. An immunoassay method for detecting a polysaccharide antigen present on a cell surface of a gram-positive bacterium in a sample, the method comprising the following steps (1) to (4) sequentially performed in the presence of a cyclic oligosaccharide:
(1) contacting the sample with a nitrite compound,
(2) reacting the nitrite compound with an organic acid to produce nitrous acid,
(3) extracting a polysaccharide antigen present on the cell surface of the gram positive bacterium in the sample with the nitrous acid, and
(4) detecting the polysaccharide antigen with an antibody.
2. The immunoassay method according to claim 1 , wherein steps (1)-(4) are performed using an immunoassay device with a sample addition part, an antigen extracting part that contains the organic acid, a labeling substance retaining part, a chromatographic medium part, and a detection part; and
wherein step (1) further comprises preparing the sample by bringing an analyte into contact with an analyte dilution solution, and supplying the sample to the sample addition part of the immunoassay device; wherein the cyclic oligosaccharide, the nitrite compound, or mixtures thereof are contained in any one or both of the analyte dilution solution and the sample addition part; and
wherein the nitrous acid produced in step (2) is generated by the reaction of the organic acid and the nitrite compound in the antigen extracting part.
3. The immunoassay method according to claim 1 , wherein the cyclic oligosaccharide is α-cyclodextrin, β-cyclodextrin, γ-cyclodextrin, or a derivative thereof.
4. The immunoassay method according to claim 2 wherein the nitrite compound is an organic nitrite.
5. The immunoassay method according to claim 2 wherein the organic acid is an organic carboxylic acid.
6. The immunoassay method according to claim 1 , wherein the extraction is performed under a pH condition with a pH of 6.5-7.0.
7. The immunoassay method according to claim 1 , wherein the gram-positive bacterium is a hemolytic streptococcus.
8. The immunoassay method according to claim 2 wherein the nitrite compound is an organic nitrite compound.