Cocktail of genetically diverse lytic phages reduces uropathogenic Escherichia coli colonization in mouse urinary...

Urinary tract infections (UTIs) caused by uropathogenic Escherichia coli (UPEC) are one of the most common bacterial infections in humans. The rise of multidrug-resistant UPEC strains increases the urgent need for alternative treatment. Two diverse lytic bacteriophages (phages), SR02 and SR04, recently exhibited an in vitro anti-UPEC activity. In this study, we reported the interplay among UPEC, phages, and the microenvironment of mammalian urinary tract in UTI phage therapy using both in vitro (human bladder cell line) and in vivo (murine acute UTI) models. A gentamicin protection invasion assay was performed in UPEC-infected human bladder cells (UM-UC-3). Both monophages and the phage cocktail significantly reduced UPEC invasion into UM-UC-3 with a synergistic effect between SR02 and SR04. Female C57BL/6 mice were transurethrally infected with 10⁷ colony-forming units of UPEC, and 2 h later, 10⁸ plaque-forming units of monophages and cocktail were single transurethrally administered to the mouse bladder. At 24 h post-UPEC infection, the cocktail significantly reduced UPEC colonization in the mouse bladder and kidney, but not in the urine. The synergism between SR02 and SR04 was observed only in the mouse bladder. Both monophages and cocktail markedly reduced UPEC ascension into mouse kidneys without a synergism or robust tissue proinflammatory cytokine gene expression. However, increased polymorphonuclear cell infiltration was observed in the bladders of SR04-treated mice. In conclusion, we report the contribution of different host urinary tract microenvironments (urine, bladder, and kidney) in the outcomes of UTI phage therapy with two lytic phages and their combination.