PLACIDE trial summary: Allen SJ et al. conducted a multicenter, randomized, double blind, placebo-controlled trial to assess the efficacy of probiotics in preventing antiobiotics associated (AAD) or C.diff associated diarrhea (CDAD) in elderly hospitalized patients. Over 2,941 elderly patients with age >65 and exposure to antibiotics were enrolled and randomized to either a probiotic therapy or placebo therapy. The primary outcome of the PLACIDE trial was diarrhea onset within 8 weeks (if antibiotics assocaited) or 12 weeks if C.diff associated. The results showed no difference in outcomes and thus the study concluded that adding probiotics does not prevent AAD or CDAD.