Microbiome Composition by Pyrosequencing in Mesenteric Lymph Nodes of Rats with CCI4-induced Cirrhosis

Background: The cross talk between the gut microbiota and the immune system, which is essential to maintain homeostasis, takes place at the intestinal lymphoid tissue such as the mesenteric lymph nodes (MLNs). Here, we investigated the presence of bacterial DNA in MLNs of control and cirrhotic rats and its relationship with inflammatory responses. Methods:The MLN microbiome of cirrhotic rats with ascites, which was induced by carbon tetrachloride (CCI4), was compared to that of control rats using quantitative real-time PCR and pyrosequencing of the 16S rRNA gene. Cytokines in blood samples were assessed by ELISA. Results: Unexpectedly, sequence analysis revealed a high microbial diversity in the MLNs of both control and cirrhotic rats with Proteobacteria as one of the most dominant phylum. CCI4-induced liver injury was not associated with a change in bacterial load, but it was linked to a decrease in microbial diversity (p<0.05) and alterations in the microbial community in MLNs. A high proportion of Bifidobacterium animalis was also positively correlated with elevated interleukin-10 expression (p = 0.002, false discovery rate = 0.03, r = 0.94). Conclusions: For the first time, the high microbial diversity observed in MLNs of both controls and CCI4-induced cirrhotic rats provides evidence that bacterial translocation is more than a mere dichotomic phenomenon. (C) 2013 S. Karger AG, Basel