Probiotic paradox: Saccharomyces cerevisiae fungemia after S. boulardii use in severe pancreatitis.

Background: Saccharomyces boulardii is a widely used probiotic for managing antibiotic-associated diarrhea and other gastrointestinal disorders. While considered safe in immunocompetent individuals, its use in critically ill patients has been increasingly associated with invasive fungal infections, particularly Saccharomyces cerevisiae fungemia. Case presentation: We report the case of a 46-year-old male admitted with severe necrotizing biliary pancreatitis, complicated by pancreatic necrosis, portal vein thrombosis, and a suspected duodenal fistula. Following emergency necrosectomy, the patient required prolonged ICU care with enteral and parenteral nutrition via jejunostomy and central venous catheter. On postoperative day 7, he developed watery diarrhoea and was started on S. boulardii (Econorm) probiotics. By day 14, he developed high-grade fever, hypotension, and leucocytosis. Blood cultures from both central and peripheral lines grew S. cerevisiae, confirmed by MALDI-TOF. The isolate was sensitive to amphotericin B, fluconazole, and caspofungin. The probiotic was discontinued, central line removed, and caspofungin initiated, resulting in clinical improvement and sterile follow-up cultures. Discussion and conclusion: Though rare, fungemia due to S. boulardii can be life-threatening, particularly in ICU settings where multiple risk factors coexist. Proposed mechanisms include gut translocation and catheter contamination during probiotic handling. This case underscores the need for caution in using yeast-based probiotics in critically ill patients. Lactobacillus-based formulations are safer alternatives. Strict infection control, microbiology communication, and heightened clinical awareness are essential to mitigate risk.