Combating multidrug-resistant uropathogenic E. coli using lytic phages, enhancing antibiotic synergy and inhibiting biofilms.

The global emergence of multidrug-resistant Escherichia coli (MDR E. coli), driven by excessive antibiotic use and environmental persistence, poses a major threat to public health. Bacteriophages (phages) have garnered renewed interest as targeted biocontrol agents against such pathogens. In this study, we isolated and characterized two lytic phages, EC.W1-1 and EC.W15-3, specifically targeting diverse sequence types (STs) of MDR E. coli. Both phages belong to the family Straboviridae and genus Tequatrovirus. They demonstrated remarkable stability across pH 2-10 (4 h) and temperatures below 80 °C (1 h), and exhibited potent in vitro lytic activity at various multiplicities of infection (MOIs, 10-0.001). One-step growth curves revealed short latent periods (10-15 min) and moderate burst sizes (64-83 PFU/cell). Genome analysis showed sizes ranging from 37,736 to 123,792 bp, with G + C contents of 35.6%-37.2%, and no virulence or antibiotic resistance genes were detected, underscoring their safety profile. Functional annotation indicated coding sequences related to structural proteins, DNA replication, transcription, repair, and lytic functions. Importantly, the phages maintained partial activity in mouse and human serum and exhibited intracellular persistence in murine macrophages, supporting their biological stability. Notably, combined treatment of phages with sub-lethal antibiotic doses effectively inhibited extended-spectrum β-lactamase (ESBL)-producing and carbapenem-resistant E. coli (CREC). Moreover, both phages efficiently disrupted biofilms formed by different MDR E. coli STs. Collectively, these findings highlight the strong therapeutic potential of EC.W1-1 and EC.W15-3, offering a promising alternative or adjunct to antibiotics in combating MDR E. coli infections.