Abstract: This review includes a total of three studies (one cross-over and two parallel RCTs) which involved 110 participants. All three studies looked at intravesical instillation of a low virulent Escherichia coli (E. coli) strain in reducing the risk of symptomatic UTI in participants with neuropathic bladder, predominantly from SCI. Two studies used the E. coli 83972 strain and one study used the E. coli HU2117 strain. We did not find any RCTs involving other probiotics or other routes of administration for preventing UTI in people with neuropathic bladder. There was consistency in definition of symptomatic UTI in all three studies. Symptoms that all studies considered were relevant to diagnose UTI were adequately defined. All three studies defined microbiological diagnosis of symptomatic UTI. Asymptomatic bacteriuria was not considered an outcome measure in any of the included studies; however it was defined in two studies to establish successful inoculation. It is uncertain if the risk of symptomatic UTI is reduced with bladder inoculation using E. coli because the certainty of the evidence is very low (3 studies, 110 participants: RR 0.32, 95% CI 0.08 to 1.19; I2 = 82%). Two studies reported adverse events. One study reported one episode of autonomic dysreflexia. One study reported three symptomatic UTI occurring in two patients, and two studies mentioned the absence of septicaemia and pyelonephritis. Intravesical instillation was reported as "generally safe". One study reported high attrition rates in participants due to the need to adhere to strict instillation protocols. The overall quality of the studies was poor. All three studies had high risk of attrition bias due to failure of an intention-to-treat analysis which undermines the randomisation process and weakened the results of the studies. All three studies also had high risk of reporting bias. In this review, there were no studies identified addressing oral probiotics in preventing UTI in people with neuropathic bladder. It is uncertain if the risk of symptomatic UTI is reduced in people with neuropathic bladders via intravesical instillation of non-pathogenic E. coli as data were derived from small studies with high risk of bias. Although very minimal levels of harm was reported with this procedure, due to variable success rates, the need for strict adherence to instillation protocols together with high attrition rates in these studies, it is doubtful bladder instillation will be a widely accepted intervention in its current form. It is recommended that further appropriately powered RCTs with more robust methodological reporting be carried out.

Plain-language summary: We conducted a literature review up to March 2017 and three studies were included according to our selection criteria. The three studies reported data on 110 participants. All three studies investigated whether introducing probiotics directly into the bladder to create a non-harmful colony will prevent urinary tract infections in people with bladder dysfunction, predominantly people with spinal cord injury. Two studies reported that this method was generally safe. This review found that generally, the studies were poor quality with high risk of bias. We found the effectiveness of colonisation with probiotics in preventing bladder infection in people with bladder dysfunction is uncertain. Furthermore, the success of colonisation was variable, and the colonisation process is invasive and demands a high level of commitment on the part of the participant. We did not identify any studies investigating whether other probiotics and other administration routes is effective in preventing urinary tract infections in people with bladder dysfunction. It is uncertain if probiotics prevent urine infections in people with bladder dysfunction after a nervous system injury. Further robustly designed studies are necessary.