Integrated immunomagnetic separation and catalase-inhibited colorimetry for rapid visual detection of Staphylococcus aureus

Staphylococcus aureus , is a prominent foodborne pathogen, that presents a significant threat to public health. The development of a rapid screening procedure remains an urgent priority, as conventional approaches are time-consuming, operationally complex, and poorly adaptable to field use. In this study, we integrated immunomagnetic separation technology (IMS) with an intracellular catalase activity-based inhibition colorimetric system for S. aureus detection. Specifically, egg yolk immunoglobulin Y (IgY) was conjugated with magnetic nanoparticles to create capture probes, enabling the specific and efficient isolation of S. aureus from complex food matrices and overcoming the low specificity of the traditional catalase test. A 3,3',5,5'-tetramethylbenzidine-horseradish peroxidase-hydrogen peroxide colorimetric system was then established for signal visualization. The intracellular catalase of S. aureus inhibited this reaction, producing distinct and easily observable color changes, offering a clear advantage over the bubble formation required in conventional catalase testing. This dual-functional strategy, combined with simplified sample preprocessing, eliminated the need for specialized instruments. The modified catalase-based assay visually detected S. aureus at concentrations as low as 10 3 CFU/mL in spiked milk samples within 75 minutes. Moreover, by simply substituting the antibody, the platform can be readily adapted to detect other catalase-positive pathogens, broadening its diagnostic utility. Overall, this cost-effective, user-friendly, and field-deployable approach shows strong potential for food safety monitoring. • A colorimetric method was developed for rapid detection of Staphylococcus aureus. • The detection limit reached 10 3 CFU/mL in a spiked milk sample within 75 min. • The strategy shows potential for on-site screening of catalase-positive bacteria.