Isolation and characterization of two novel oral bacteriophages with anti-biofilm activity against Cutibacterium acnes

Bacteriophage therapy offers a promising solution to combat antibiotic-resistant infections, yet its potential against biofilm-associated pathogens in oral diseases remains underexplored. This study investigates the opportunistic bacterium Cutibacterium acnes, an overlooked contributor to dental implant and prosthetic joint infections. Biofilms formed by C. acnes are highly resilient and resistant to antibiotics, complicating treatment. Two novel lytic bacteriophages, Ristretto and Corretto, targeting C. acnes, were isolated from human saliva, with morphological analysis confirming their classification as siphoviruses. Their genome sequencing revealed no harmful antimicrobial resistance or virulence genes, making them suitable for therapeutic use. Remarkably, phage Corretto demonstrated a broad host range and achieved near-complete eradication of mature biofilms across multiple C. acnes strains, outperforming Ristretto in efficacy and strain coverage. The activity of these phages was dosage-dependent and varied across bacterial strains, revealing potential strain-specific resistance mechanisms within biofilms. These findings highlight bacteriophage therapy's potential to disrupt persistent biofilms where antibiotics fail, offering a new approach for treating biofilm-driven infections in dental and medical implantology. This study underscores the need for further research into phage-based strategies to address the growing global challenge of antimicrobial resistance and improve outcomes in biofilm-related diseases.