Ecological study on the intestinal bacteria flora of patients with diarrhea.

In the intestinal flora of patients with diarrhea, a close correlation exists between a decrease in numbers of anaerobes and a reduction in levels of short-chain fatty acids. The drastic reduction of intestinal volatile fatty acids (VFAs) accompanying decreased counts of anaerobes during the diarrheal state and the increase in pH thought to arise from these changes result in increased fecal water content. Our data suggest that free bile acids and VFAs may be factors controlling intestinal bacterial populations in vivo, especially in enteric infections. Thus the role of nonspecific factors such as VFAs, which are among the bile acid metabolites produced by anaerobic intestinal bacteria, deserves emphasis in the evaluation of protective mechanisms provided by the intestinal flora against enteric infections.