Abstract: Objective: This study aimed to develop an immunochromatographic test strip (ICS) for the rapid detection of Staphylococcus aureus (S. aureus) and to evaluate its practical applicability in milk matrices. Methods: Immunoprobes were synthesized by conjugating colloidal gold with polyclonal antibodies specific to S. aureus. After optimizing the reaction parameters, we constructed the ICS. The sensitivity, specificity, and accuracy of the assay were rigorously validated, followed by performance testing in spiked milk samples. Results: The visual detection limit of the strip was 104 CFU/mL, and the quantification limit was 9.52 × 103 CFU/mL. The linear range is 104 to 107 CFU/mL. Conclusion: The developed ICS demonstrated high specificity for S. aureus with no cross-reactivity against other common foodborne pathogens. The assay was successfully applied to milk samples, with recoveries ranging from 82.72% to 112.78%. Characterized by its speed, convenience, and reliability, this method provides an effective tool for the rapid on-site monitoring of S. aureus in dairy products.

Key words: Staphylococcus aureus; colloidal gold; rapid detection