Phagomagnetic immunoassay for the rapid detection of Salmonella

This work explores the use of the phage P22 in a phagomagnetic immunoassay for the rapid detection of Salmonella. The covalent attachment of wild-type phages was performed on two different magnetic carriers: carboxyl-activated magnetic nanoparticles (300 nm) and tosyl-activated magnetic microparticles (2.8 μm). The bacteria were captured and preconcentrated by the phage-modified magnetic particles, followed by the detection using specific anti-Salmonella antibodies conjugated to horseradish peroxidase as an optical reporter. Outstanding selectivity and sensitivity was obtained with this approach, achieving detection limits of 19 CFU mL(-1) in 2.5 h without any pre-enrichment, in milk samples. Moreover, if the samples were pre-enriched for 6 h, the method was able to detect as low as 1.4 CFU in 25 mL of milk. Therefore, the proposed strategy based on the combined use of phagomagnetic separation with immunological labeling is promising as a rapid and simple method for food safety.