Identification of oral bacteria in the gut and foot ulcer of patients with diabetes mellitus – A secondary analysis of whole-metagenome and meta-transcriptomic microbiome data

Abstract Background: Gum disease (periodontitis) is a risk factor for diabetes mellitus and treatment has been shown to improve markers of glucose management. The translocation of oral bacteria to the gut or other tissues (i.e., foot ulcer) may contribute to the development and progression of diabetes mellitus Aims: This secondary analysis of metagenomic and meta-transcriptomic studies within the last ten years (2011-2021) aims to identify bacteria of oral origin in the gut and foot ulcers of patients with diabetes mellitus and explore a potential pathway how gum disease and diabetes mellitus are connected.Method: An electronic search was conducted in Medline on the Ovid platform (updated in June 2022). Studies with whole-metagenomic or meta-transcriptomic data at the species level in populations of all ages and genders with type 1 or type 2 diabetes and diabetic complications such as diabetic foot ulcers were included. Patient demographics, diabetic status and bacteria detected in faecal or foot ulcer samples were extracted from a total of 7 included studies.Results: Out of 9612 (gut) and 9180 (foot ulcer) microbial species identified from the selected studies, 266 bacteria were identified as oral origin. These oral bacteria compromised 5.96% in foot ulcer and 1.51% in the gut. Eleven bacteria of oral origin were only found in patients with diabetes mellitus compared to healthy individuals of the Human Microbiome Project (HMP). These bacteria included key oral pathogens such as Tannerella forsythia, Prevotella nigrescens and Prevotella intermedia. Conclusion: The continuous swallowing of oral bacteria may be a reservoir for gut microbiota and its dysregulation, which has been linked to diabetes. Clinical trials aimed at simultaneously detecting and analysing gut and oral bacteria are required.