Randomised controlled trials (RCTs) that compared probiotics with placebo in adult patients who received antibiotics and that measured C. difficile infection as one of the outcomes were eligible for inclusion. Eligible trials had to be blinded and to be published in full articles. The outcome of interest was C. difficile infection rate.
Most of the included trials evaluated Lactobacillus species in combination with other Lactobacillus species or other organisms. Four trials evaluated Saccharomyces boulardii and one trial evaluated Lactobacillus species alone. Most of included patients were adult hospitalised patients. Where reported, duration of antibiotic treatment ranged from three days to 21 days. Four trials explicitly stated prior C. difficile infection as an exclusion criterion and three trials screened patient stools at baseline for C. difficile. Most studies were conducted in USA, UK and Canada.
The authors did not state how many reviewers assessed studies for inclusion.