Escherichia coli bacteriophage vB_EcoS_MS2 effectively prevents biofilm formation but shows limited activity against mature biofilms.

Pathogenic Escherichia coli biofilms pose a significant challenge in veterinary and clinical settings due to their high antibiotic resistance. This study characterizes the E. coli bacteriophage vB_EcoS_MS2 as a potential targeted biocontrol agent against these pathogens. Host range determination revealed high specificity, with vB_EcoS_MS2 lysing only select E. coli strains and demonstrating superior replication efficiency (Efficiency of Plating: 112.57%) on strain C4 compared to its propagation host, MS2. While nutrient limitation strongly induced biofilm formation in in vitro assays, phage vB_EcoS_MS2 demonstrated potent prophylactic activity, inhibiting initial biofilm development by over 70% across all tested concentrations (10⁴-10⁹ PFU/mL). Conversely, the phage showed limited and transient efficacy in eradicating mature, 48-hour-old biofilms under the tested conditions. Whole-genome sequencing confirmed a 40,209 bp circular genome belonging to the class Caudoviricetes, encoding a robust holin-endopeptidase lytic cassette without carrying known antimicrobial resistance determinants. These findings indicate that while vB_EcoS_MS2 is highly effective for prophylactic biofilm prevention, complementary strategies may be required to clear established biofilms.