Characterization of a newly isolated broad-host-range lytic phage WEN7 against multidrug-resistant clinical Pseudomonas aeruginosa strains

Abstract

Introduction Pseudomonas aeruginosa is a Gram-negative opportunistic pathogen with intrinsic and acquired resistance to multiple classes of antibiotics. Phage therapy has emerged as a promising approach to combat multidrug-resistant bacterial infections. Methods In this study, a lytic P. aeruginosa phage, WEN7, was isolated from hospital wastewater using PAO1-SZ1 as the host. We systematically characterized its morphology, growth kinetics, stability, host range, whole-genome sequence and bactericidal performance. Results WEN7 formed clear plaques. Transmission electron microscopy revealed an icosahedral 66 nm head attached to a contractile tail, with intact virions captured in both fully extended (140 nm total tail length) and sheath-contracted (60 nm) states—this classic myoviral morphology places the phage within the class Caudoviricetes. One-step growth curve analysis revealed a latent period of approximately 25 min and an average burst size of about 165 PFU/cell. WEN7 remained stable under various temperatures, pH values, UV exposure, and ethanol concentrations. The phage displayed a broad host range, lysing 19 of the 29 clinical P. aeruginosa isolates tested (65.5%). Its genome is a circular double-stranded DNA molecule of 66,379 bp with a GC content of 55.62%. Notably, no known antibiotic resistance genes or virulence factors were annotated. WEN7 shares the highest genomic similarity with the Pseudomonas phage PCCM_PaP004 (genus Pbunavirus). At low multiplicities of infection, WEN7 showed strong bactericidal activity in both milk and hospital wastewater. Discussion Together, these results indicate that phage WEN7 is a promising candidate for phage therapy against multidrug-resistant P. aeruginosa infections.