Exploring the potential of combining phage therapy and cell-free culture supernatant of lactic acid bacteria for treating common pathogenic bacteria in a Galleria mellonella burn wound infection model

Burn injuries are a significant public health concern worldwide and are often associated with infection-related mortality. Existing treatment methods make the healing process challenging, highlighting the need for new and effective therapeutic approaches. In this study, a burn wound infection model was developed in Galleria mellonella larvae using common burn wound pathogens, and the therapeutic potential of combining cell-free extracts (CFEs) from lactic acid bacteria (LAB) with lytic bacteriophages was investigated. Infections were established using the prevalent burn pathogens such as Staphylococcus aureus, Pseudomonas aeruginosa, Enterococcus faecalis, and Escherichia coli. The treatments involved CFEs derived from Lactobacillus reuteri and L. plantarum, iin combination with broad-host-range phages ΦECO 35, ΦSA 43, ΦPAG 2, and ΦEFE 2. The phages were characterized morphologically by electron microscopy, as well as by parameters such as host range, thermal and pH stability, latent period, and burst size. The larvae (180–250 mg) were divided into four groups (n ≥ 10): control (phosphate buffer), phage only, CFE only, and phage+CFE combination. After thermal injury and infection, treatments were administered as single or double doses, and survival rates were monitored over 96 hours. According to the findings, in P. aeruginosa infection, survival at 96 hours was approximately 75% with a single dose of the phage+CFE combination and increased to 90% with a double dose. In E. coli infection, survival was about 85% with a single dose and reached 90% with a double dose. In S. aureus infection, survival was 80% with a single dose and at least 85% with a double dose, while in E. faecalis infection, survival was approximately 70% with a single dose and about 75% with a double dose. In the phosphate buffer control groups, survival remained between 0-20%. These results suggest that the combination of lytic phages and LAB CFEs exerts a synergistic effect in the treatment of burn infections, improving survival rates. Notably, survival increased markedly with two-dose applications. The combined the