A virulent and temperate phage cocktail synergizes with antibiotics against multidrug-resistant Pseudomonas aeruginosa

Abstract

The rapid emergence of multidrug-resistant bacteria necessitates antimicrobial strategies that constrain resistance while preserving efficacy. Phage cocktails are typically composed exclusively of virulent phages, whereas the therapeutic potential of temperate phages remains largely unexplored. Here, we evaluate a two-phage cocktail combining a virulent (ARP5) and a temperate (ARP3) phage against a multidrug-resistant Pseudomonas aeruginosa clinical isolate (PaAK08). While ARP5 alone achieved strong bacterial suppression and ARP3 displayed limited efficacy, the combined cocktail sustained > 98% suppression across multiplicities of infection for 30 h. Resistance profiling revealed no cross-resistance between phages, consistent with receptor independence. Phenotypic and genomic analyses of resistant mutants identified alterations in surface-associated structures, including glycosyltransferase-linked loci, and ARP3 prophage integration events. Phage ratio optimization maintained suppression at reduced concentrations, with statistical analysis supporting additive interactions. Notably, co-administration with subinhibitory tobramycin or ofloxacin produced synergistic suppression, achieving complete inhibition for 48 h with ofloxacin. Together, these findings demonstrate that virulent–temperate phage combinations can function compatibly, expand therapeutic design frameworks, and potentiate antibiotic activity against multidrug-resistant P. aeruginosa .