Faecal bacterial microbiota in patients with cirrhosis and the effect of lactulose administration

Background: Gut microbiota may be altered in patients with cirrhosis, and may further change after administration of lactulose. We studied the composition of gut microbiota in patients with cirrhosis and assessed the effect on it of lactulose administration. Methods: Stool specimens were collected from 35 patients with cirrhosis (male 26; median [range] age: 42 [29-65] years) and 18 healthy controls (male 14; 44.5 [24-67] years); 21 patients provided another specimen after lactulose administration for 55 [42-77] days. For each, a DNA library of V3 region of bacterial 16S ribosomal RNA was subjected to paired-end Illumina sequencing. Inter-specimen relationship was studied using principal co-ordinate analysis. Abundances of various bacterial taxa, and indices of alpha and beta diversity were compared, between patients and controls, and between specimens collected before and after lactulose. Results: Gut microbiota from cirrhosis patients and controls showed differential clustering, and microbiota from patients with cirrhosis had less marked alpha diversity. Abundances of dominant phyla (Bacteroidetes, Firmicutes and Proteobacteria) were similar. However, patients with cirrhosis had lower abundances of five phyla, namely Tenericutes, Cyanobacteria, Spirochaetes, Elusimicrobia and Lentisphaerae, and differences in abundances of several families and genera than in controls. Lactulose administration did not lead to any change in alpha and beta diversities, species richness and abundances of various bacterial taxa in gut microbiota. Conclusions: Gut microbiota in cirrhosis differ from healthy persons and do not change following lactulose administration. The latter suggests that the effect of lactulose on hepatic encephalopathy may not be related to alteration in gut microbiota.