Isolation, characterization, and genomic analysis of a novel lytic bacteriophage with potent antibiofilm activity against multidrug-resistant Acinetobacter baumannii.

The rapid rise of multidrug-resistant Acinetobacter baumannii (MDR A. baumannii) poses a serious threat in healthcare settings, as these bacteria can cause infections that are untreatable with conventional antibiotics. This crisis has driven the search for alternative therapies, one of which is bacteriophages. In this study, we isolated a novel bacteriophage, vB_AbaM_EA1 (E7 for short), from wastewater and evaluated its potential activity against clinical MDR A. baumannii strains. Phage E7 successfully infects (27.5%) of the 40 clinical MDR A. baumannii isolates we tested. Laboratory characterization suggested that E7 is a highly efficient lytic phage, rapidly attaching to bacterial cells and producing 1000 new viral particles.A key finding was its potent activity against bacterial biofilms, a major source of persistent infections. Not only did Phage E7 effectively prevent the formation of new biofilms, but more importantly disrupted mature ones, which typically confer higher resistance to antibiotics.Genome sequencing confirmed that Phage E7 is a new member of the Obolenskvirus genus and that its genome lacks genes encoding bacterial toxins, antibiotic resistance, or lysogenic factors, indicating a mandatory safety profile for therapeutic use. Furthermore, E7 remained stable across a broad temperature range (-20 to 45 °C) and pH values (5-9) that it might encounter during storage and administration. In conclusion, Phage E7 is a stable, safe, and highly effective candidate for phage therapy against infections by MDR A. baumannii. Its ability to target both planktonic bacteria and biofilms makes it a promising candidate for future development into clinical applications.