Now, however, a randomized, controlled trial (RCT) of a lactobacilli/bifidobacteria combination in antibiotic-exposed adults over 65 years of age showed…..no difference in AAD (10.8% in treatment vs. 10.4% in control group) or C. difficile (0.8% vs. 1.2%). The trial was fairly large (almost 3000 patients enrolled), large enough that one would hope to see a difference in AAD, but the overall C. difficile rate was too low to say much (confidence interval for RR was 0.34-1.47). One major finding hidden in Table 3 of the manuscript: the treatment group had a statistically-significant increase in flatus (insert fart noises here).
What to do with this seemingly contradictory finding? A single negative RCT, performed in a narrowly defined population (inpatients over the age of 65) doesn’t exclude a potential benefit from probiotic use in other groups or if tested in a larger population with a higher baseline incidence of C. difficile.
This does serve as another reminder, though, that when it comes to probiotics, there’s no substitute for the real thing.