We applied the concept of using benign bacteria to prevent symptomatic infection, so-called bacterial interference, by deliberately colonizing the bladder of patients with SCI with a non-pathogenic prototype of Escherichia coli (strain 83972). The preliminary results of our VA-funded study that compared the rates of symptomatic UTI in patients with SCI while colonized with E. coli 83972 vs. historical rates of symptomatic UTI prior to study enrollment indicated that deliberate colonization of the bladder of patients with SCI with E. coli 83972 is safe and very promising as to its ability to prevent symptomatic UTI. However, before this innovative approach of bacterial interference can be successfully applied in the population of patients with SCI, it is essential to: (A) confirm the ultimate efficacy of bacterial interference by conducting a prospective, randomized, placebo-controlled clinical trial (objective #1); and (B) enhance the practicality of applying this innovative approach in SCI patients by delineating the bacterial and host factors that can promote successful colonization with E. coli 83972 (objectives #2-3).