Enhancement of the antimicrobial properties of bacteriophage-K via stabilisation using oil-in-water nano-emulsions

Bacteriophage therapy is a promising new treatment that may help overcome the threat posed by antibiotic-resistant pathogenic bacteria, which are increasingly identified in hospitalised patients. The development of biocompatible and sustainable vehicles for incorporation of viable bacterial viruses into a wound dressing is a promising alternative. This paper evaluates the anti-microbial efficacy of Bacteriophage K against Staphylococcus aureus over time, when stabilised and delivered via an oil-in-water nano-emulsion. Nano-emulsions were formulated via thermal phase inversion emulsification, and then bacterial growth was challenged with either native emulsion, or emulsion combined with Bacteriophage K. Bacteriophage infectivity, and the influence of storage time of the preparation, were assessed by turbidity measurements of bacterial samples. Newly prepared Bacteriophage K / nano-emulsion formulations have greater anti-microbial activity than freely suspended bacteriophage. The phage loaded emulsions caused rapid and complete bacterial death of three different strains of Staphylococcus aureus. The same effect was observed for preparations that were either stored at room temperature (18 - 20°C), or chilled at 4°C, for up to 10 days of storage. A response surface design of experiments was used to gain insight on the relative effects of the emulsion formulation on bacterial growth and phage lytic activity. More diluted emulsions had a less significant effect on bacterial growth, and diluted bacteriophage-emulsion preparations yielded greater antibacterial activity. The enhancement of bacteriophage activity when delivered via nano-emulsions has yet to be reported. This prompts further investigation into the use of these formulations for the development of novel anti-microbial wound management strategies.