Eight RCTs, involving 997 participants in total, were included.
The study quality scores ranged from 3 to 5; all randomised studies were double-blind.
Prevention of CDAD (1 RCT, 138 participants): there was no difference between placebo and probiotic groups in the percentage of patients with CDAD after therapy.
Treatment of CDAD (3 RCTs, 300 participants): one RCT reported an overall beneficial effect of probiotics that was largely due to a significant effect in a subgroup of participants with recurrent CDAD. Another RCT suggested a positive response to probiotics in a patient subgroup receiving high-dose vancomycin who were more likely to have severe CDAD. A further small RCT found no difference between placebo and probiotic groups.
Prevention of antibiotic-associated diarrhoea with prevention of CDAD as a secondary outcome (4 RCTs, 559 participants): all 4 RCTs found probiotic therapy to have no significant effect on the prevention of CDAD; in one of the studies the data on CDAD was not from a comparison of randomised patients.
Adverse effects (7 RCTs): no serious adverse effects were associated with probiotics in any of the studies.