Effect of Lactobacilli on Urinary Indican Excretion in Gnotobiotic Rats and in Man

The effect of Lactobacillus species on urinary indican excretion in two types of gnotobiotic rats (GBH-9 and GB-5) and in man was studied. L. salivarius, L. plantarum and L. casei colonized in the cecum and colon of both types of rats at levels of 10⁷ to 10⁸ per gram of contents following one-dose oral administratron and caused a significant reduction in urinary indican excretion, whereas two strains of L. acidophilus which colonized at low levels (10⁴ to 10⁵/g) did not reduce indican excretion. Daily feeding of Lactobacillus concentrates caused a further significant reduction in indican excretion which was corrected by tryptophan intake, even in the case of L. acidophilus. There was a clear relationship between fecal lactobacillus counts and urinary indican. A significant reduction of indican secretion was obtained only when the fecal counts of lactobacilli exceeded 10^7.4/g in rats. L. casei also had an effect in man, reducing urinary excretion of indican and p-cresol. Reduction in indican excretion seems to be accompanied by decreasing fecal tryptophanase activity in rats and man. A negative correlation was also obtained between fecal resident lactobacilli and urinary indican in man (r = ? 0.532, n = 28, p<0.01). Subjects with lactobacilli at a level of 10⁶/g or more excreted less indican than those harboring the bacteria at levels below 10⁵/g.