AIM: To assess the effects of Sb on fecal flora and shortchain fatty acids (SCFA) in patients on long-term TEN.METHODS: Ten patients (3 females, 7 males, 59±5.5 years),on TEN for a median of 13 mo (1-125), and 15 healthy volunteers (4 females, 11 males, 32±2.0 years) received Sb (0.5 g bid PO) for 6 d. Two stool samples were taken before, on the last 2 d and 9-10 d after treatment, for SCFA measurement and for culture and bacterial identification.Values (mean±SE) were compared using sign tests and ANOVA.RESULTS: Fecal butyrate levels were lower in patients(10.1±2.9 mmol/kg) than in controls (19.2±3.9, P= 0.02).Treatment with Sb increased total fecal SCFA levels in patients (150.2±27.2 vs 107.5±18.2 mmol/kg, P = 0.02)but not in controls (129.0±28.6 vs 113.0±15.2 mmol/kg,NS). At the end of treatment with Sb, patients had higher fecal butyrate (16.0±4.4 vs 10.1 [2.9] mmol/kg, P = 0.004).Total SCFAs remained high 9 d after treatment was discontinued. Before the treatment, the anaerobe to aerobe ratio was lower in patients compared to controls (2.4±2.3 vs69.8±1.8, P = 0.003). There were no significant changes in the fecal flora of TEN patients.CONCLUSION: Sb-induced increase of fecal SCFA concentrations (especially butyrate) may explain the preventive effects of this yeast on TEN-induced diarrhea.