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.

Background/Objectives: The viral pandemic caused by the SARS-CoV-2 virus has affected millions of people. However, it was noticed that high mortality was often a result of bacterial co-infections. One of the main pathogens responsible for secondary infections in patients with viral respiratory tract infections, including COVID-19, is Staphylococcus aureus. In recent years, the number of infections caused by drug-resistant strains of S. aureus has been growing rapidly, often exceeding the number of infections caused by antibiotic-sensitive strains. In addition, biofilm-related infections are more difficult to treat due to the lower sensitivity of biofilm structure to antibiotics. Bacteriophages are seen as alternative treatment of bacterial infections. Therefore, in our work, we have analyzed the efficacy of three Kayviruses against S. aureus strains isolated from COVID-19 patients. Methods: We analyzed the ability of tested phages to remove S. aureus biofilm both from polystyrene plates as well as from the surface of pulmonary epithelial cells. Results: We have observed that tested Kayviruses had a broad host range. Furthermore, phages were able to effectively reduce biofilm biomass and number of viable cells in pure culture. During our research, none of the tested phages was shown to have a negative effect on cell viability and were able to inhibit the negative effect S. aureus had on cell condition. Conclusions: Our results show tested phages were effective in reducing the biofilm of S. aureus strains isolated from COVID-19 patients, had no adverse effect on lung epithelial cell viability. Therefore, it should be recognized that the properties of three studied Kayviruses give them an advantage in the selection of phages for treatment of staphylococcal infections.

Background/Objectives: Skin and soft tissue infections (SSTIs) represent a significant clinical challenge, largely due to the high prevalence of antibiotic-resistant Staphylococcus aureus, particularly methicillin-resistant S. aureus (MRSA). Treatment is further complicated by biofilm formation, which reduces antibiotic efficacy. The limitations of conventional therapies highlight the need for alternative approaches. Phage therapy has emerged as a promising biological strategy; however, its effectiveness may be constrained by factors such as phage instability and biofilm regrowth. This study aimed to enhance phage-based treatment by combining a newly isolated phage, vB_Sau-E, with lactoferrin (Lf), a multifunctional protein of the innate immune system. Methods: Phage vB_Sau-E was characterized in terms of its infection dynamics and lytic activity. Biocompatibility was further examined using human skin cell lines. The potential effect of Lf was assessed by evaluating its impact on phage infectivity and stability under a range of environmental conditions and by checkerboard assay. Results: Phage vB_Sau-E belongs to the Silviavirus genus in the Herelleviridae family. It was shown to infect 12 out of 22 tested clinical MRSA isolates, with 10 strains identified as good hosts. The phage has a ~30 min life cycle, and ~50 progeny virions are released after bacterial cell lysis. We have also observed that Lf increased plating efficiency and enhanced phage stability at a pH of 5.5 and at −20° C. It also proved to have an additive antibacterial effect, though this was observed to be strain-dependent. Conclusions: Lactoferrin functions as a stabilizing adjuvant for phage vB_Sau-E. Its additive effect supports the development of more effective, biofilm-targeting therapies for staphylococcal SSTIs.