Characterization of bacteriophages infecting multidrug-resistant uropathogenic Escherichia coli strains

Uropathogenic Escherichia coli (UPEC) is the most common causative agent of urinary tract infections, and strains that are resistant to antibiotics are a major problem in treating these infections. Phage therapy is a promising alternative approach that can be used to treat infections caused by polyresistant bacterial strains. In the present study, 16 bacteriophages isolated from sewage and surface water were investigated. Phage host specificity was tested on a collection of 77 UPEC strains. The phages infected 2-44 strains, and 80% of the strains were infected by at least one phage. The susceptible E. coli strains belonged predominantly to the B2 phylogenetic group, including strains of two clones, CC131 and CC73, that have a worldwide distribution. All of the phages belonged to class Caudoviricetes and were identified as members of the families Straboviridae, Autographiviridae, and Drexlerviridae and the genera Kagunavirus, Justusliebigvirus, and Murrayvirus. A phage cocktail composed of six phages - four members of the family Straboviridae and two members of the family Autographiviridae - was prepared, and its antibacterial activity was tested in liquid medium. Complete suppression of bacterial growth was observed after 5-22 hours of cultivation, followed by partial regrowth. At 24 hours postinfection, the cocktail suppressed bacterial growth to 43-92% of control values. Similar results were obtained when testing the activity of the phage cocktail in LB and in artificial urine medium. The results indicate that our phage cocktail has potential to inhibit bacterial growth during infection, and they will therefore be preserved in the national phage bank, serving as valuable resources for therapeutic applications.