A visual colorimetric assay based on phage T156 and gold nanoparticles for the sensitive detection of Salmonella in lettuce

In this study, a new technique was developed for visual and precise identification of Salmonella using phage T156-mediated aggregation of gold nanoparticles. The phage binds to gold nanoparticles in a dispersed and stable state under high NaCl concentrations. When Salmonella is introduced, the phage specifically recognizes and adsorbs the targeted bacteria, causing the AuNPs to undergo a discoloration reaction resulting in aggregation, which enables Salmonella visualization. The method has a detection range of 3.8 × 101–3.8 × 109 CFU/mL and a limit of detection of 38 CFU/mL and can produce results in approximately 80 min. The technique was also tested on field samples, including spiked lettuce, and was found to be accurate with a recovery rate of 81.0–119.2% and relative standard deviations ranging from 3.3% to 14.7%. Notably, this technique utilizes phages as recognition elements in colorimetric methods, offering simplicity, speed, and the ability to effectively distinguish between live and dead Salmonella. It demonstrates remarkable sensitivity, specificity, and accuracy. Furthermore, it presents a novel avenue for the rapid detection of other pathogenic bacteria.