Background The microbial populations of the human intestinal tract and their relationship to specific diseases have been extensively studied during the last decade. However, the characterization of the human bile microbiota as a whole has been hampered by difficulties in accessing biological samples and the lack of adequate methodologies to assess molecular studies. Although a few reports have described the biliary microbiota in some hepatobiliary diseases, the bile microbiota of healthy individuals has not been described. With this in mind, the goal of the present study was to generate fundamental knowledge on the composition and activity of the human bile microbiota, as well as establishing its potential relationship with human bile-related disorders. Results Human bile samples from the gallbladder of individuals from a control group, without any record of hepatobiliary disorder, were obtained from liver donors during liver transplantation surgery. A bile DNA extraction method was optimized together with a quantitative PCR (qPCR) assay for determining the bacterial load. This allows the selection of samples to perform functional metagenomic analysis. Bile samples from the gallbladder of individuals suffering from lithiasis were collected during gallbladder resection and the microbial profiles assessed, using a 16S rRNA gene-based sequencing analysis, and compared with those of the control group. Additionally, the metabolic profile of the samples was analyzed by nuclear magnetic resonance (NMR). We detected, for the first time, bacterial communities in gallbladder samples of individuals without any hepatobiliary pathology. In the biliary microecosystem, the main bacterial phyla were represented by Firmicutes , Bacteroidetes , Actinobacteria , and Proteobacteria . Significant differences in the relative abundance of different taxa of both groups were found. Sequences belonging to the family Propionibacteriaceae were more abundant in bile samples from control subjects; meanwhile, in patients with cholelithiasis members of the families Bacteroidaceae , Prevotellaceae , Porphyromonadaceae , and Veillonellaceae were more frequently detected. Furthermore, the metabolomics analysis showed that the two study groups have different metabolic profiles. Conclusions Our results indicate that the gallbladder of human individuals, without diagnosed hepatobiliary pathology, harbors a microbial ecosystem that is described for the first time in this study. Its bacterial representatives and metabolites are different from those detected in people suffering from cholelithiasis. In this regard, since liver donors have been subjected to the specific conditions of the hospital’s intensive care unit, including an antibioti...

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The high morbidity and mortality of hepatocellular carcinoma (HCC) has encouraged the search for new biomarkers to be used alongside alpha-foetoprotein (AFP) and imaging tests. The aim of this study was to evaluate the clinical contribution of protein induced by vitamin K absence or antagonist-II (PIVKA-II) for HCC monitoring after liver transplantation (LT) and compare it with AFP, a routinely used tumour marker. A total of 46 HCC patients (Milan criteria) were enrolled in this study. Serum levels of PIVKA-II and AFP were measured before and after transplantation. Clinical features were determined for all the patients that were included. Significant correlations were found between PIVKA-II expression levels and some clinicopathological features, such as tumour size and number of pre-transplant transarterial chemoembolizations (TACEs). Serum levels of PIVKA-II and AFP decreased significantly after LT and increased in patients with tumour recurrence. Serum PIVKA-II levels may play an important role in predicting disease severity. Furthermore, monitoring PIVKA-II levels in HCC transplant recipients reflects the tumor early recurrence after transplantation and could be used, complementing AFP and imaging tests, as a novel biomarker of this pathology.