Background: Bacterial translocation from the gut plays an important role in the pathophysiology of acute-on-chronic liver failure (ACLF). However, gut dysbiosis in ACLF was not widely documented in previous studies.

Aim: This research characterized the fecal microbiota in patients with ACLF and analyzed the temporal stability of gut microbiota during illness.

Methods: Fecal microbiota of 79 ACLF patients (42 patients were followed in the next 4 weeks after the first visit for longitudinal study) and 50 healthy controls was analyzed by 16S ribosomal DNA pyrosequencing.

Results: There was a marked difference between the ACLF group and the control group. The overall microbial diversity and richness were significantly lower in ACLF than in controls. ACLF patients had lower abundance of Bacteroidaceae, Ruminococcaceae, and Lanchnospiraceae, but higher abundance of Pasteurellaceae, Streptococcaceae, and Enterecoccaceae. The relative abundance of Lachnospiraceae was obviously decreased in ACLF patients with hepatic encephalopathy. The gut microbiota kept relatively stable in a short term after the onset of ACLF. The use of antibiotics only showed moderate impacts on the gut microbiota. The relative abundance of Pasteurellaceae and Model of End Stage Liver Disease score were independent factors predicting mortality rate. Network analysis comparison showed robust correlations between specific bacterial families (Ruminococcaceae and Lachnospiraceae) and inflammatory cytokines (interleukin [IL]-6, tumor necrosis factor alpha, IL-2) in ACLF patients.

Conclusions: These data suggest gut dysbiosis in ACLF and its predictive value for mortality. The results thus open up the possibility of designing diagnostic biomarkers and targeted probiotics aimed at decreasing mortality in ACLF.