Observational studies have suggested a relationship between the plasma concentration of indoxyl sulfate (IS) and p-cresyl sulfate (PCS), small gut-derived ‘uremic solutes’, and the high incidence of uremic cardiomyopathy in patients with end-stage renal disease (ESRD). IS and PCS are derived from the metabolism of dietary components (tryptophan and tyrosine) by gut bacteria. This pilot study was designed to examine the effects of a poorly absorbable antibiotic (vancomycin) on the plasma concentration of two gut-derived ‘uremic solutes’, IS and PCS, and on the composition of the gut microbiome.

Plasma concentrations of IS and PCS were measured by MS-HPLC. The gut microbiome was assessed in stool specimens sequenced for the 16S rRNA gene targeting the V4 region.

The pre-dialysis mean plasma concentrations of both IS and PCS were markedly elevated. Following the administration of vancomycin (Day 0), the IS and PCS concentrations decreased at Day 2 or Day 5 and returned to baseline by Day 28. Following vancomycin administration, several changes in the gut microbiome were observed. Most striking was the decrease in diversity, a finding that was evident on Day 7 and was still evident at Day 28. There was little change at the phylum level but at the genus level, broad population changes were noted. Changes in the abundance of several genera appeared to parallel the concentration of IS and PCS.

These findings suggest that alteration of the gut microbiome, by an antibiotic, might provide an important strategy in reducing the levels of IS and PCS in ESRD.