Exploring Local Reservoirs for Bacteriophages with Therapeutic Potential against ESKAPE Pathogens

Bacteriophage therapy is a promising strategy used to treat antimicrobial-resistant or persistent bacterial infections. More recently, the clinical utility of bacteriophages has been rediscovered due to the rise of multi-drug resistance and their potential use in clinical practice as an additional treatment option. In this study, local municipal wastewater facilities, hospital wastewater systems, and freshwater reservoirs were evaluated for the presence of lytic bacteriophages. These phages were isolated using conventional phage isolation techniques: water sample collection and processing, pre-enrichment with the host bacteria, the spot test, and the double-layer method. Plaques were selected according to their morphology and lytic activity on the target bacteria. Clinical isolates and reference strains belonging to the ESKAPE group were the targets during phage isolation. A total of 210 lytic plaque morphotypes with activity against ESKAPE strains were isolated from 22 water samples. Each isolate was qualitatively evaluated for its ability to inhibit the growth of its host strain. Thirty-one translucent plaques with apparent lytic activity were selected for purification. Of these, 87.1% were isolated from wastewater samples, and 12.9% were isolated from flowing freshwater. Specifically, the phages isolated from the freshwater samples targeted Staphylococcus aureus strains, and no phage from Enterococcus faecium strains was isolated. In conclusion, wastewater samples are a suitable source for the isolation of exogenous lytic phages; however, freshwater could be considered an alternative source for the isolation of lytic phages.