Stimulating effect of lactoferrin on antibacterial efficacy of vB_SauM-A phage against multi-drug resistant strains of Staphylococcus aureus

Bacteriophages are seen as one of the most promising alternatives to antibiotic treatment in fight against drug resistant bacteria. However, as the interest in therapeutic potential of phages grew it became clear that even phages have their limitations. Narrow spectrum of activity, preference for bacteria in specific phase of metabolic activity or development of resistance mechanisms to phages may influence the efficacy of phage treatment. Therefore, in order to avoid those effects pairing bacteriophages with other antimicrobials is being researched. In our work we have paired staphylococcal phage vB_SauM-A with lactoferrin, a protein with proven antimicrobial activity and we have studied how this combination affected phage performance. We have observed that addition of 1 mg/mL of lactoferrin resulted in increased efficacy of plating of phage lysate. We have also noticed that it has influenced phage adsorption and life cycle kinetics on two out of four tested Staphylococcus aureus strains. Finally, in vivo experiment with Galleria mellonella showed that phage-lactoferrin mixture had higher therapeutic effect than the phage alone. Therefore, we assume that supplementation of phage cocktails with lactoferrin may increase the efficacy of the treatment. However, the subject requires more studies using different groups of phages and pathogens.