Sensitive Enzyme-Amplified Electrical Immunoassay for Protein A-Bearing Staphylococcus aureus in Foods JOY L. BROOKS, BAHRAM MIRHABIBOLLAHI, AND ROHAN G. KROLL* Department of Microbiology, Agricultural and Food Research Council Institute of Food Research, Reading Laboratory, Shinfield, Reading RG2 9AT, United Kingdom Received 7 May 1990/Accepted 8 August 1990
An amperometric electrochemical immunoassay specific for protein A-bearing Staphylococcus aureus was developed. The method was based on a sandwich immunosorbent assay and incorporated an enzyme amplification step, using a NAD-specific redox cycle generating NADH (C. H. Stanley, A. Johannsson, and C. H. Self, J. Immunol. Methods 83:89-95, 1985). Reduction of the mediator, ferricyanide, was dependent on the initial concentration of antigen. The final potential was measured by using a Pt disk electrode polarized at +0.8 V to the Ag/AgCl reference electrode. The assay was rapid (4 h) and generated protein A- and cell (S. aureus)-dependent signals. The system was highly sensitive and could detect 10 pg of protein A ml-l and
Sensitive enzyme-amplified electrical immunoassay for protein A-bearing Staphylococcus aureus in foods.
An amperometric electrochemical immunoassay specific for protein A-bearing Staphylococcus aureus was developed. The method was based on a sandwich imm...