Data on Clostridium difficile infection were sufficient only for the comparison between MBP+OAB versus MBP alone, with data from 14 studies, including 10 RCTs53,55,61,62,65,67,69,75,78,80 and 4 cohort studies.43,54,68,82 No difference in C difficile infection rates were seen when all evidence was considered (RR 0.94, 95% CI 0.55–1.61, P = 0.81, I2 = 37%), nor when just RCT studies or cohort studies alone were analyzed (RR 0.79, 95% CI 0.21–2.96, P = 0.72, I2 = 10% and RR 0.97, 95% CI 0.54–1.75, P = 0.92, I2 = 64%, respectively). The gene discussed is MBP; the disease is clostridium difficile infection.