The authors were interested in the effect of hepatitis C virus (HCV) infection on gut microbiota and whether this impact the progression of chronic hepatitis C (CHC). They examined faecal samples from 166 CHC patients and compared them with those from 23 healthy participants, examining the gut microbiota community with 16S ribosomal RNA gene sequencing. CHC patients either had persistently normal serum alanine aminotransferase without evidence of liver cirrhosis (LC, PNALT, n=18), chronic hepatitis (CH, n=84), LC (n=40) and hepatocellular carcinoma with LC (n=24). The authors found that the bacterial diversity was lower in patients with HCV infection compared with healthy controls, with a decrease in the order Clostridiales and an increase in Streptococcus and Lactobacillus. Microbiota dysbiosis had already appeared by the PNALT stage, with a transient increase in Bacteroides and Enterobacteriaceae. The predicted metagenomics also demonstrated an increase in the urease gene, mostly encoded by viridans streptococci, during CHC progression, which is consistent with a significantly higher faecal pH in CH and LC patients than in healthy participants or those in the PNALT stage. Therefore HCV infection is associated with gut dysbiosis, even in patients with mild liver disease. The overgrowth of viridans streptococci can also account for the hyperammonaemia seen in CH and LC.
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