Urinary tract infections are among the most prevalent microbial diseases and their financial burden on society is substantial. The use of bacteriophages against bacterial pathogens has gained over the last years a renewed interest, because of the continuing increase in antibiotic resistance worldwide. Thus, the aim of this study is to investigate the efficacy of intravesical bacteriophage treatment to normalize urine culture compared to intravesical placebo or standard antibiotic treatment.