Behaviour of Saccharomyces boulardii in recurrent Clostridium difficile disease patients

Background: Despite recent interest in therapeutic microorganisms taken orally, little is known about the pharmacodynamics of these agents in a target population of patients with disease. The present study reports the stool concentrations of Saccharomyces boulardii in a patient population with Clostridium difficile disease (CDD) and correlates stool concentrations with efficacy. Methods: Patients with recurrent CDD all received a 10-day standard antibiotic regimen together with 28 days of S. boulardii or placebo. Stool samples were collected from patients at various time points and assayed for S. boulardii. Results: The mean concentration of S. boulardii of patients who recurred was 2.5 x 10⁴ CFU/g compared to 1 x 10⁶ CEU/g in patients that did not recur (P = 0.02). Patients with low yeast concentrations in their stools (< 10⁴/g) recurred more often (14/15, 93%) compared with patients with higher levels (19/35, 54%, P = 0.007). Clearance of S. boulardii was rapid; only 4% had positive stools 3 days after stopping dosing. Conclusions: After chronic dosing of S. boulardii, patients with low stool concentrations had a higher likelihood of recurrence of CDD. Stool concentrations were also lower during periods of diarrhoea. These results show the importance of characterizing the dynamics of a therapeutic microorganism in patients with disease, as kinetic studies in healthy volunteers may not give a true reflection of the disturbed microecology in the disease state.