Employment of the Phage Cocktail as a Species-Specific Recognition Agent for Wide-Spectrum Detection of Bacterial Strains.

Phages have already been employed to detect bacteria because of their specific recognition capability and strong infectious activity toward their host. However, the reported single-phage-based techniques are inevitably restricted by false negative results that arose from extremely high strain specificity of phages. In this study, a cocktail composed of three () phages was prepared as a recognition agent to broaden the recognition spectrum for detecting this bacterial species. A total of 155 clinically isolated strains of collected from four hospitals were adopted to test its recognition spectrum. A superior recognition rate of 91.6% for the strains was achieved due to the complementarity of the recognition spectra of the three phages composed of the cocktail. However, the recognition rate is as low as 42.3-62.2% if a single phage is employed. Based on the wide-spectrum recognition capability of the phage cocktail, a fluorescence resonance energy transfer method was established for detecting strains by employing fluorescein isothiocyanate labeled to the phage cocktail and Au nanoparticles labeled to -mercaptophenylboronic acid as energy donors and acceptors, respectively. The detection process can be completed within 35 min, with a wide dynamic range of 5.0 × 10-1.0 × 10 CFU/mL. The application potential was verified by applying it to quantitate in different sample matrixes. This pioneer work opens an avenue for achieving wide-spectrum detection of different strains belonging to the same bacterial species with the phage cocktail.