Isolation and characterization of genetically diverse phages against Escherichia coli for the development of broad-spectrum, resistance-suppressive, and antibiofilm phage therapeutics

To address the growing concern of drug resistance in bacterial pathogens, exploring alternative antibacterial options is crucial. Phages, natural predators of bacteria, play a vital role in regulating bacterial populations and offer potential for therapeutic applications. The inherent potential of phages to lyse bacterial cells, owing to their life cycle, has been utilized in therapeutic applications, a concept known as phage therapy. In this study, we report the isolation and comprehensive characterization of four E. coli lytic phages (KKE5S, KKE7M, KKE8S, and KKE16M) from diverse environmental sources and assess their antibacterial efficacy. The isolated phages form a clear plaque on bacterial lawns, demonstrating their lytic nature. The absence of antibiotic resistance and virulence genes ensured their safety for potential therapeutic use. Host range analysis revealed that phages KKE7M and KKE16M are broad-spectrum, capable of infecting both E. coli and Salmonella species. Phylogenetic and comparative analysis revealed that isolated phages are genetically diverse and belong to different families. Except for KKE8S, the other three isolated phages represent a novel species within their respective genera. The application of the four-phage cocktail results in enhanced suppression of resistance as compared to single-phage treatment. Additionally, the antibiofilm activity of phages encoding depolymerases was tested against a mature E. coli MG1655 biofilm. Scanning microscope analysis revealed disrupted biofilm and lysed cells after phage treatment. This study isolated and characterized four genetically diverse phages that expand the pool of isolated novel phages and highlight their therapeutic potential for treating biofilm-associated E. coli .