Oral bacterial load in autoimmune liver diseases: possible role or coincidence?

Background and aims: Several factors seem be involved in the pathogenesis of autoimmune liver disease (ALD), such as bacteria or bacterial components. Some studies highlighted the role of an oral bacterium, P. gingivalis, in the pathogenesis of rheumatoid arthritis and in the induction of NASH. We evaluated if there was a correlation between oral bacteria and some features of ALD. Methods: We analyzed 50 patients with ALD, 22 with autoimmune hepatitis (AIH) and 28 with primary biliary cirrhosis (PBC), 94% females, median age 61 years, median disease duration 7.5 years, 18% with cirrhosis, 66% responders to treatment, 40% with concomitant autoimmune diseases, and 46 health controls matched for sex and age. Patients and controls were subjected to cytobrush of the tongue. Exclusion criteria were antibiotic use in the previous week, mouthwash use on the day of inclusion. The study was conducted with the local ethics committee approval and informed consent was obtained from all subjects. Bacterial DNA (BD) obtained from the tongue biofilm was quantified using a computer RNA-DNA and expressed as ug/ml of sample.For each analysis, three distinct biological replicas were done, and quantitative data were expressed as mean ± SD. Results: BD amount was greater in ALD than in controls (1834.10 vs. 881.75, p < 0.0001). There was no correlation between BD amount and age, disease duration, histological findings and biochemical parameters, except for alkaline phosphatase (p = 0.05). The presence of cirrhosis, response to therapy and the immunosuppressive drug use did not affect BD amount. Finally, patients with concomitant autoimmune diseases had a greater BD amount than the other (2053.54 vs. 1687.60) but without significance (p = 0.57). Conclusion: Our study showed an unspecified role of oral bacteria in patients with autoimmune liver diseases. Further analysis will be needed to assess if there are differences in the microbial population.