Positives

• In antibiotic co-therapy studies, S. boulardii CNCM I-745 users had fewer adverse events than antibiotics alone, with only one premature withdrawal in a controlled trial PMC microbiota study.
  
  
• A patient-facing reference notes the strain has decades of use preventing antibiotic-associated and traveler's diarrhea, common GI flares for long-haulers on rounds of antibiotics MedlinePlus.
  
  

Negatives

• Drug references warn of rare bloodstream fungemia in immunocompromised patients or those with central lines, a flag for severe long-haulers using ports Medscape.
  
  

Hurdles & Side Effects

• Common start-up effects include flatulence, constipation, and thirst, which can be hard to distinguish from baseline Long COVID gut symptoms WebMD.