Isolation and characterization of a novel lytic bacteriophage Ecolivirus Myo-P293 targeting avian pathogenic Escherichia coli.

A novel lytic bacteriophage, Ecolivirus Myo‑P293 (P293), targeting avian pathogenic Escherichia coli (APEC), was isolated from duck farm sewage in Jiangsu, China. P293 formed clear plaques approximately 2 mm in diameter and displayed the characteristic morphology of Myoviridae family, with an icosahedral head (~ 70 nm) and a contractile tail (~ 100 nm), as observed under transmission electron microscopy. Adsorption assays showed that over 70% of phages adsorbed to host cells within 5 min. One-step growth analysis revealed a latent period of approximately 30 min and a burst size of 244 ± 36 PFU per infected cell. P293 exhibited stability across a pH range of 5–9 and at temperature between 20 and 40 °C, but its infectivity was significantly reduced when exposed to temperature ≥ 60 °C or 60% ethanol. The phage effectively disrupted mature E. coli biofilms, achieving approximately 45% clearance after 24 h of treatment, and also inhibited biofilm formation in a dose-dependent manner. Whole-genome sequencing of P293 revealed an 89.5 kb double-stranded DNA genome encoding 95 open reading frames (ORFs), including modules related to structure, replication, lysis, and host interaction. Approximately 40% of the encoded genes are annotated as hypothetical proteins. Phylogenetic and comparative genomic analyses placed P293 within the unclassified Felixounavirus clade, closely related to Escherichia phage wV8 and Salmonella phage Felix O1, while displaying distinct tail fiber gene signatures associated with host specificity. These findings support the potential of P293 as a candidate for phage-based biocontrol strategies against APEC in poultry production.