Optimisation and Development of Quantum Dot-Labelled Bacteriophages for the Detection and Killing of Poultry Associated Salmonella spp.

The global demand for poultry is increasing, and associated with this is an increasing number of foodborne diseases, with Salmonella spp. being one of the main causative agents. To counter the spread of disease and reduce dependence on antibiotics, there need to be effective diagnostic and treatment strategies. One way in which this can be done is via the use of phage-based therapies and diagnostics.

Here, a labelling strategy to conjugate bacteriophages with quantum dots (QDs) was achieved, via the chemical biotinylation of phages, allowing for streptavidin-QD conjugates to bind to their surface. These QDs could be stably bound to the phages without significantly impairing behaviour. It was shown that these QD-phages could be used to detect Salmonella cells via flow cytometry and optical tweezer analyses, although the level of bacterial detection was found to be low, the foundations have been laid for future work relating to the use of these QD-phages for bacterial detection-based work.

Furthermore, in relation to therapies targeting Salmonella spp. using phages, progress was made in a few areas. The first was by showing the novel application of how the photoexcitation of the designed QD-phages, resulted in the effective killing of Salmonella cells in vitro, due to the potential generation of reactive oxygen species from the QDs. Moreover, it was shown that phages and carbon quantum dots could work synergistically towards killing Salmonella based on this same principle. Finally, it was shown that phages isolated from a poultry farm in India had lytic activity towards different strains of Salmonella isolated from farms in the UK, including various antibiotic-resistant strains, highlighting their potential use in phage-based therapies targeting Salmonella spp.