AIM: To assess the effects of Sb on fecal flora and short-chain 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 vs 69.8 +/- 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. (C) 2005 The WJG Press and Elsevier Inc. All rights reserved.