Isolation of Bacteriophages and Their Lytic Profile From River and Waste Water Samples in South Western Uganda

Abstract

Background: Bacteriophages are found almost everywhere in the environment, such as water, soil, and air, among others. They are effective against a wide range of pathogens because they are highly specific. This study aimed to identify phages from river and wastewater samples in south-western Uganda and determine their lysis profile against selected clinical bacterial isolates. Materials and methods: Four different locations (Mbarara city and Ntungamo, Kabale, and Kisoro districts) in south-western Uganda were chosen for the collection of river and wastewater for isolation of potential phages. The culture and double agar overlay method was used to detect the lytic bacteriophages. Isolated phages were purified after diluting them in saline magnesium (SM) buffer, then centrifuged at 3,000 rpm for 10 minutes, and filtered through a 0.22 um syringe filter. After purification, the filtrate was used to determine the phage lytic activity, host range activity (using the spot method), and thermal stability (using the double agar overlay method). Results: A total of 17 phages were isolated using Escherichia coli WG5 as the host. The phage concentration ranged from 5.5 x 10 6 -7.6 x 10 11 pfu/mL. All the isolated phages were used for host range determination on Salmonella spp., Morganelli morganii, extended-spectrum beta-lactamase (ESBL) E. coli, Proteus mirabilis, Citrobacter freundii, Coryne bacteria spp., and Serratia marcescens bacterial isolates. Of the 17 phages, ECWG5_I_MbraKat_OJ_25 and ECWG5_RKirUS_OJ_25 phages were the most effective against the tested bacterial strains, with 75% lytic ability. These two phages could lyse ESBL E. coli. The isolated phages were stable at 4 °C and 37 °C, and their dilution end point range was 10 -6 to 10 -10 , suggesting that the phage stocks were still potent and able to infect bacteria at relatively high dilutions. Conclusion: The study isolated 17 phages from wastewater and the river water, which showed lytic activity against selected clinical Gram-positive and Gram-negative bacterial isolates. This study offers preliminary insights into the environmentally isolated phages, enabling researchers to further characterize and assess their potential application in phage-based clinical interventions, particularly for the management of drug resistant pathogenic bacteria.