Highly sensitive and selective colorimetric determination of Staphylococcus aureus via chicken anti-protein A IgY antibody

Abstract

Staphylococcus aureus (S. aureus) is a food-borne pathogenic organism that causes an array of infectious diseases ranging from superficial skin infections to potentially fatal diseases. Thus quantitative detection of S. aureus with high selectivity and sensitivity is of great significance. In this study, Staphylococcus protein A (SPA), which is specifically secreted on the surface of S. aureus, was selected as an epitope. On the basis of the specific recognition of SPA by chicken anti-protein A immunoglobulin Y (IgY), a facile colorimetric immunoassay for the detection of S. aureus was established. To the best of our knowledge, this is the first time chicken anti-protein A IgY has been utilized as an antibody pair for the quantitative detection of S. aureus. Chicken anti-protein A IgY was conjugated with magnetic particles for bacterial capture. Then horseradish peroxidase (HRP) labeled chicken anti-protein A IgY was employed as the revealing partner to perform a sandwich format assay, followed by an HRP catalyzed colorimetric reaction. Optimized detection conditions produced a calibration curve for S. aureus ranging from 7.8 × 10² CFU mL⁻¹ to 2.0 × 10⁵ CFU mL⁻¹ with a detection limit of 2.3 × 10² CFU mL⁻¹ (3σ) in phosphate-buffered saline (PBS). The detection limits (3σ) in spiked samples were very close to those in PBS. The entire assay was accomplished in less than 60 min and no cross-reactivity with the other tested bacterial species was observed. These results demonstrate that the proposed method is effective for rapid and selective screening of S. aureus in food samples.