Metagenomic Approach Studing The Taxonomic And Functional Diversity Of The Fecal Mcirobiota In Patients With Liver Cirrhosis

Liver cirrhosis is the pathologic end stage of chronic liver disease. In China and some other Asian countries, hepatitis B virus infection is one of the leading causes. On the other hand, alcohol-related cirrhosis is a major cause of morbidity and mortality in Western countries. Increasing evidence suggests that gut flora is implicated in the pathogenesis of liver cirrhosis complications. It is well recognized that the gut flora may play an important role in the development of complications of liver cirrhosis, including bacterial infections, the hyperdynamic circulatory state, and hepatic encephalopathy. Although it is widely accepted that cirrhosis leads to characteristic changes in intestinal microbiota, this has not been easily demonstrated in previous studies using culture-dependent methods. Over the past decade, culture-independent methods have been applied to studies of human gut bacterial diversity where the majority of the bacteria are not culturable. These methods are helping scientists to better understand the role of human intestinal microbiota on human health and illness with a broader and less biased viewThe aim of our study is to characterize the fecal microbial community in patients with alcoholic liver cirrhosis, HBV-related liver cirrhosis and healthy controls. The fecal microbial community was analyzed by454pyrosequencing of the16S ribosomal RNA (16S rRNA) V3region followed by functional gene array GeoChip. Community-wide changes of fecal microbiota in liver cirrhosis were observed compared with healthy controls. The proportion of phylum Bacteroidetes was significantly reduced (p=0.008), while Proteobacteria and Fusobacteria were highly enriched in the cirrhosis group (p=0.001and0.002, respectively). Enterobacteriaceae (p=0.001), Veillonellaceae (p=0.046), and Streptococcaceae (p=0.001) were prevalent in cirrhotic patients at the family level. A positive correlation was observed between Child-Pugh (CP) score and Streptococcaceae (R=0.386, p=0.02). Lachnospiraceae significantly decreased in the cirrhotics (p=0.004), and correlated negatively with CP score (R=-0.49, p=0.002). By Partial Least Square Discriminate Analysis (PLS-DA), we identified149operational taxonomic units (OTUs) as key phylotypes that responded to cirrhosis, and most of them were Lachnospiraceae (65OTUs), Streptococcaceae (23OTUs), and Veillonellaceae (21OTUs).GeoChip data showed that the microbial community functional composition and structure were dramatically altered in the alcoholic cirrhosis and HBV-related cirrhosis. A variety of functional genes relevant to nutrient metabolism were significantly under-represented in cirrhotic patients than in controls, including genes for amino acid metabolism, lipid metabolism, cofactor biosynthesis and isoprenoid biosynthesis. Significant correlations were observed between functional genes and Child-Pugh score, such as aspartate-ammonia ligase gene,transaldolase gene, adenylosuccinate synthetase gene and IMP dehydrogenase gene.The454data showed significant increase of Prevotellaceae in alcoholic cirrhosis patients than in HBV-related cirrhosis patients. Various microbial functional genes involved in organic remediation, stress response, antibiotic resistance and virulence were highly enriched in the alcoholic cirrhosis group compared with control group and HBV-related cirrhosis group. Long term consumption of alcohol may stimulate microbial activities in stress response, organic remediation, antibiotic resistance and virulence.Conclusion:Fecal microbial communities are distinct in cirrhotic patients compared with healthy individuals. The prevalence of potentially pathogenic bacteria, such as Enterobacteriaceae and Streptococcaceae, with the reduction of beneficial populations such as Lachnospiraceae in cirrhotics may affect prognosis. Also, cirrhosis may have distinct influences on metaobolic potential of fecal microbial communities, which may have an effect in the progression of malnutrition.