DEVELOPMENT OF A SPECTROPHOTOMETRIC IMMUNO-AGGLUTINATION ASSAY FOR QUANTITATION OF IGG FOR ESCHERICHIA-COLI O157

A direct spectrophotometric immuno-agglutination assay for quantitatio n of specific Escherichia coli O157 IgG was developed. Initial linear rates of increase in absorbance at 550 nm as a result of agglutination were found to increase with bath cell and antiserum concentrations. O ptimum conditions consisted of 1 x 10(8) cells/ml, 40 degrees C, and 0 .005 NI phosphate buffer (PB) containing 0.05% NaCl and 0.02% sodium a zide at pH 7.4. A completely linear increase in absorbance was obtaine d with affinity purified IgG under optimum conditions of the assay. Th e useful range of the assay was between 13 and 104 mu g of O157 specif ic IgG per ml of reaction mixture.