Table 2.

Studies characterizing the composition of the gut microbiota in liver cirrhosis.

Author Reference	Country	Study Design	Participants	Changes in the Composition of the Gut Microbiota in Liver Cirrhosis	Key Findings
[54]	China	Case-control	36 cirrhosis 24 healthy controls	↑ Proteobacteria ↑ Fusobacteria ↑ Enterobacteriacea ↑ Veillonellacea ↑ Streptococcaceae ↓ Bacteroidetes ↓ Lachnospiraceae	Fecal microbiome composition was altered in patients with cirrhosis compared to healthy individuals, indicating there is dysbiosis ↑ Enterobacteriaceae and Streptococcaceae may affect cirrhosis prognosis
[55]	United States	Prospective cohort study	25 cirrhosis: 17 with HE 8 without HE 10 controls	↑ Bacteroidetes ↑ Veillonellaceae in HE ↑ Enterobacteriacea ↑ Alcaligeneceae ↑ Porphyromonadacea ↑ Fusobacteriaceae ↓ Ruminococcaceae ↓ Lachnospiraceae	Dysbiosis was found in patients with HE compared to healthy individuals Certain bacterial families were associated with endotoxemia, impaired cognition, and inflammation in liver cirrhosis patients in HE
[57]	China	Case-control	26 cirrhosis patients with MHE 25 cirrhosis patients without MHE 26 healthy controls	↑ Streptococcus salivarius in HE ↑ Streptococcaceae ↑ Veillonellaceae	Streptococcus salivarius was positively correlated with ammonia accumulation in MHE patients
[61]	United States and Japan	Cross-sectional study	47 cirrhosis 14 healthy controls	↑ Enterobacteriaceae ↓ Lachnospiraceae ↓ Ruminococcaceae ↓ Blautia	↑ Pathogenic bacteria due to gut dysbiosis in cirrhotic patients altered bile acid composition
[58]	China	Case-control	98 cirrhosis 83 controls	↑ Proteobacteria ↑ Veillonella ↑ Streptococcus ↓ Bacteroidetes	In liver cirrhosis, there was an invasion of the gut by oral bacterial species
[64]	Unites States	Case-control	87 with HE 40 healthy controls	↑ Enterobacteriaceae ↓ Lachnospiraceae ↓ Ruminococcaceae	Specific bacterial families were associated with astrocytic and neuronal MRI changes Gut dysbiosis in cirrhosis was linked with systemic inflammation, elevated ammonia levels, and neuronal dysfunction
[62]	China	Case-control	30 cirrhosis 28 healthy controls	↑ Veillonella ↑ Megasphaera ↑ Dialister ↑ Atopobium ↑ Prevotella ↑ Firmicutes	↑ Oral bacteria in duodenal mucosal microbiota in cirrhotic patients
[65]	China	Cross-sectional study	36 cirrhosis 20 healthy controls	↑ Firmicutes ↓ Bacteroidetes	↑ Microbial dysbiosis in cirrhotic patients with Child-Pugh scores > 5 led to slower small bowel transit
[66]	Austria	Case-control	90 cirrhosis: 50 on PPI therapy 40 not on PPI therapy	↑ Streptococcus salivarius ↑ Veillonella parvula	↑ Gut dysbiosis in cirrhotic patients with long-term PPI therapy
[67]	Spain	Prospective cohort study	182 cirrhosis	↑ Enterococcus ↑ Streptococcus in ACLF ↑ Faecalibacterium ↑ Ruminococcus ↑ Eubacterium in decompensated patients	As cirrhosis progressed from compensated to uncompensated to ACLF, there was a linear progression in reduction in gene and metagenomic richness
[56]	Russia	Case-control	48 cirrhosis 21 healthy controls	↑ Enterobacteriaceae ↑ Proteobacteria ↑ Lactobacillaceae ↓ Firmicutes ↓ Clostridia	Severe dysbiosis was an independent risk factor for death Levels of Clostridia and Bacilli determined death within a year Levels of Proteobacteria and Enterobacteriaceae determined the long-term prognosis (death over the subsequent three years)

ACLF, acute-on-chronic liver failure; HE, hepatic encephalopathy; MHE, minimal hepatic encephalopathy; PPI, proton pump inhibitors; ↑, increase; and ↓, decrease.