Genomic and in vitro characterization of two lytic bacteriophages infecting multidrug-resistant Erwinia sp. strain AnSW2-5.

Multidrug-resistant (MDR) Erwinia pathogens present a critical threat to global crop health and agricultural sustainability. In this study, we characterized two novel lytic bacteriophages, AnSW2-5-P-A (family Autographiviridae) and AnSW2-5-P-K (class Caudoviricetes), targeting the MDR Erwinia sp. strain AnSW2-5. Comparative genomics and TEM analysis revealed distinct virion architectures and confirmed the absence of lysogeny-associated genes, ensuring their safety as biocontrol agents. One-step growth assays demonstrated that P-A has a shorter latent period (~ 20 min), while P-K exhibits a significantly larger burst size (~ 110 PFU/cell). In co-culture assays, the dual-phage cocktail demonstrated a profound synergistic effect, achieving > 80% bacterial reduction (p < 0.05) and maintaining sustained suppression of the host for 72 h. Notably, the cocktail effectively prevented the emergence of resistant mutants, reducing the frequency of resistance (FoR) to below the limit of detection (< 10⁻⁸). These findings highlight the potential of using genetically diverse phage pairs with complementary lytic activities as a robust, resistance-suppressive biocontrol strategy against MDR phytopathogens.