Isolation, characterization and genomic analysis of three lytic bacteriophages (PBM) targeting Avian Pathogenic Escherichiacoli.

Avian pathogenic Escherichia coli (APEC) cause significant economic losses in the poultry industry, further exacerbated by the growing number of multi-drug resistance pathogens that make treating infections more difficult. To combat this, the study presents two novel Schitoviridae phages (PBM-2 and PBM-3) and a novel Straboviridae phage (PBM-1) that show significant and highly specific lytic activity against APEC strains. Moreover, the phages show significant lytic activity at MOI as low as 0.1 and show substantial thermal (4-45 °C) and acidic tolerance (pH 3-7). The PBM phages also show suitable growth parameters, with high adsorption rates (9-15 min), relatively short latent periods (20-25 min), and a good burst size (∼100 per cell). The genome sizes for the PBM phages are around 121 kb for PBM-1 and 72 kb for PBM-2 and PBM-3, with 194, 84 and 83 predicted genes, respectively. Comparative genomic analysis revealed a high sequence similarity between PBM-2 and PBM-3. Further analysis showed a high degree of relatedness of PBM-1 with Escherichia phage EPIMAM01 and Escherichia phage HP3, as well as PBM-2 and PBM-3 with Escherichia phage UE-S5b, Enterobacteria phage Bp4. Furthermore, no genes associated with antibiotic resistance, lysogeny, or known virulence factors were detected, supporting their suitability for therapeutic use. The isolation and characterization of these novel phages presents an opportunity to develop effective phage therapies against avian colibacillosis.