A SEMI-HOMOGENEOUS AMPEROMETRIC IMMUNOSENSOR FOR PROTEIN-A-BEARING STAPHYLOCOCCUS-AUREUS IN FOODS

A semi-homogeneous amperometric immunosensor specific to the protein A of Staphylococcus aureus was developed using direct electrochemical detection of phenol produced by alkaline phosphatase from phenyl phosphate. The immunosensor could reliably detect strains of protein A-bearing S. aureus in pure cultures at ca. 304 cfu/ml, and at ca. 105 cfu/g or ml in various food samples. Due to its semi-homogeneous nature, the system was very simple, easy to operate, and labour-saving. The good correlation between the amperomatric current generated by the immunosensor and plate counts illustrated the potential usefulness of this simple system. It proved to be a reliable 24-h detection method for food samples containing very low numbers of protein A-bearing S. aureus after pre-enrichment, as it was able to detect cells that could not directly be enumerated by plate counts. © 1990 Springer-Verlag.