Isolation and characterization of human skin-derived bacteriophages with antibacterial and antibiofilm activity against coagulase-negative staphylococci

Abstract Coagulase-negative staphylococci (CoNS), particularly Staphylococcus epidermidis and Staphylococcus capitis , are significant opportunistic pathogens associated with biofilm-related infections and antimicrobial resistance. Although bacteriophage therapy is a promising alternative to antibiotics, human skin-derived phages targeting clinically important CoNS remain poorly characterized. Four bacteriophages were isolated from facial skin swabs of healthy volunteers, and two (phages Se_20 and Se_42) were selected for detailed characterization. Biological characteristics, antibacterial activity, genomic features, and preliminary in vivo activity were evaluated. Both phages exhibited lytic activity against clinically relevant CoNS and reduced planktonic bacterial counts by > 3 log₁₀ CFU/mL within 4–6 h. They showed strain-dependent antibiofilm activity, inhibiting biofilm formation by up to 88.6% and reducing preformed biofilm biomass by up to 86.3%. Both exhibited a latent period of 25 min, while the burst sizes were 142 PFU/cell for Se_20 and 70 PFU/cell for Se_42. Genome analyses confirmed that phages were lytic and lacked virulence factors, antimicrobial resistance genes, and tRNA/rRNA genes. In the Galleria mellonella infection model, phage treatment increased larval survival without detectable toxicity. This study demonstrates that the human skin microbiome is a valuable source of lytic bacteriophages against CoNS and supports their further preclinical evaluation as alternative antimicrobial candidates for biofilm-associated infections.