Disclosed is the use of Bacillus subtilis QST713 (NRRL Accession Number B21661) or a mutant of Bacillus subtilis QST713 for the manufacture of a medicament for the treatment or prevention of a gastro-intestinal disorder in a human, wherein the gastro-intestinal disorder is selected from the group consisting of acute diarrhoea, Clostridium dificile-associated infection, inflammatory bowel disease, irritable bowel disorder, and antibiotic-associated diarrhoea and wherein the mutant Bacillus subtilis QST713 has sequence identity to the Bacillus subtilis QST713 of at least 98%.