Metagenomic analysis of salivary microbiota in patients with anorexia nervosa and association with functional digestive disorders (ORMICAN pilot study)

Background Patients with anorexia nervosa (AN) have intestinal dysbiosis and are frequently affected by oral and upper gastrointestinal disorders. Until now, no metagenomic sequencing data were available on oral microbiota in AN. Design This observational study enrolled 46 patients with restrictive/purging AN and 20 controls. Salivary samples were performed after fasting. DNA of oral microbiota from salivary samples was analysed by whole genome shotgun deep sequencing. The primary objective was to compare the diversity of oral microbiota between patients with AN and healthy individuals. Secondary endpoints were to assess the associations between the diversity of oral microbiota and the severity of functional digestive disorders, between patients with a restrictive type of AN and patients with a mixed/purging type and between the diversity of oral microbiota and the severity of AN. Results We observed not only a significant decrease in the alpha diversity of oral microbiota in AN patients (4.47 (4.05; 4.75)) versus controls (4.81 (4.68; 5.04)) (p=0.001) but also in gene richness (p=0.00023). There was no significant correlation (95% CI) between oral microbiota diversity and functional digestive disorders nor between patients with a restrictive type of AN and patients with a mixed/purging type of AN, nor between the diversity of oral microbiota and the severity of AN. In addition, we observed four bacterial taxa that were decreased in AN patients. Conclusion Our study highlights a decreased diversity of oral microbiota in AN patients. Future larger studies may help identify the prognostic and therapeutic value of oral microbiota in AN.