Visual detection of Staphylococcus aureus based on immunomagnetic separation and polymerase spiral reaction

Staphylococcus aureus (S. aureus) is widely distributed in the environment, which can easily lead to food contamination. Thus, it is essential to develop rapid and on-site detection of S. aureus. In the present study, an intuitive colorimetric method based on phage display technology (PDT), immunomagnetic separation (IMS), and polymerase spiral reaction (PSR) was successfully established for S. aureus detection. Peptide-2 (P2, MNVTFTT) with high affinity and specificity for S. aureus was screened by PDT. The formed P2-magnetic beads (MBs) were able to effectively enrich and isolate S. aureus from complex matrices under applied magnetic field. Then a PSR assay was developed for signal amplification and visualization and performed in a thermostatic metal bath using specific primers targeting nuc gene. The results could be observed by naked eyes with a significant color change from purple to blue. The newly developed IMS-PSR assay enabled detection of S. aureus at levels as low as 84 CFU/mL (1.5 pg) in spiked milk sample within 3 h. With all these benefits, it shows promise for rapid on-site visual detection of S. aureus.