Bilinear Staphylococcus aureus detection based on suspension immunoassay

A novelty bilinear suspension immunoassay biosensor is developed for Staphylococcus aureus specific detection. In the present study, a dual-color-based sandwich immunosensor was constructed for sensitive and selective detection of this bacterium. In this bioassay system, the monoclonal antibodies of Staphylococcus aureus were immobilized on carboxyl-modified fluorescent microspheres (PSA-R6G) which acted as a capture probe. A secondary fluorescein isothiocyanate (FITC)-labelled antibody of Staphylococcus aureus acted as a sensitive reporter antibody. After dual-labelling with R6G and FITC, the enriched Staphylococcus aureus bacteria were observed by using the multiparameter flow cytometry analysis. In this method, two regression equations were obtained with I-FITC = 1.56lgC + 4.50 and I-R6G = 1.54lgC + 2.78, respectively. It can be noted that the two slopes were very similar, which indicated the false positives decrease significantly. For general applications, the quantificational measurements of Staphylococcus aureus in milk and water samples were also carried out. The suspension immunoassay exhibited an excellent specificity to Staphylococcus aureus in contrast to conventional culture-based method.