Isolation and characterization of a Staphylococcus aureus-lytic jumbo phage LY01 and its local therapeutic efficacy in a porcine dermatitis model.

Porcine dermatitis caused by Staphylococcus aureus (S. aureus) has garnered increasing attention due to the escalating antibiotic resistance, necessitating the development of alternative therapeutic strategies. In this study, a S. aureus-lytic jumbo phage, designated as LY01, was isolated from swine farm effluent and subsequently characterized. Key findings revealed that the bacteriophage exhibited lytic activity against S. aureus with broad host specificity. LY01 possesses a short latent period (30 min), thermal stability (30°C-50°C), and pH stability (pH 5-9). Phylogenetic analysis based on genomic sequencing, combined with electron microscopy for morphological observation, classified LY01 within the phylum Uroviricota and class Caudoviricetes. Furthermore, the therapeutic effect of phage LY01 on swine dermatitis was assessed by evaluating the severity of dermatitis lesions, histopathology, hematology, changes in inflammatory factors, and microbial diversity. The in vivo results showed that local LY01 therapy significantly decreased skin bacterial loads, cutaneous inflammatory responses, and blood leukocyte counts, while improving the skin tissue-associated bacteria composition and alleviating histopathological injury in dermal samples. These findings indicate that local application of LY01 on S. aureus-induced dermatitis lesions is associated with clinical improvement, which provides a promising approach to address antibiotic resistance in treating S. aureus-induced skin infections.