A novel sensing platform for detecting Staphylococcus aureus using feline IgG as a specific recognition element

Traditional immunoassays based on mouse or rabbit immunoglobulin G (IgG) often suffer from poor specificity in Staphylococcus aureus ( S. aureus ) detection, which is primarily due to the interference from protein G-producing Streptococcus species. This study aimed to propose a sensing platform for detecting S. aureus using feline IgG immobilized on magnetic beads (MBs) as capture agents, given its high affinity for staphylococcal protein A (SPA) via its Fc region and negligible affinity for protein G to achieve specific capture of S. aureus. Horseradish peroxidase (HRP)-conjugated chicken anti-protein A immunoglobulin Y (HRP-IgY) was used as the detection antibody, which formed a dual-recognition sandwich structure (MBs-feline IgG/ S. aureus /HRP-IgY). A colorimetric signal was generated through the HRP-catalyzed oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB), enabling the quantitative detection of S. aureus . The proposed method displayed favorable linearity in the range of 6.3 × 10 2 to 8.0 × 10 4 colony-forming unit (CFU)/mL under optimized conditions, with a low detection limit of 5.3 × 10 2 CFU/mL. The entire detection procedure could be completed within 90 min. Specificity tests confirmed negative responses for common non-target bacteria. Furthermore, the method was successfully applied for S. aureus detection in milk, tap water, and apple juice with satisfactory detection limit. This platform exhibited excellent expansibility and can be further integrated with microfluidic devices, holding immense potential for point-of-care testing applications.