Saccharomyces boulardii

Tier 1 — strong evidence · Gut · C. diff · Traveller diarrhoea

S. boulardii is a non-pathogenic yeast probiotic uniquely resistant to antibacterial drugs, making it the only probiotic suitable for simultaneous use with antibiotics. The strongest evidence is for prevention of antibiotic-associated diarrhoea and C. difficile recurrence — the Cochrane review (Pillai 2008, PMID 18254055) found a significant reduction in CDiff recurrence (RR 0.59). Alharbi 2024 meta-analysis (10 RCTs, PMID 38458507) confirmed S. boulardii among the strains effective for traveller's diarrhoea prevention. Guarino 2015 (PMID 26447963) identifies it alongside L. rhamnosus GG…

Dose: 250–500 mg (5–10 billion CFU) twice daily. For AAD prevention, begin within 48 hours of starting antibiotics and continue 1 week after completing the course. For traveller's diarrhoea, begin 5 days before travel and continue throughout.