The oral microbiome of newly diagnosed tuberculosis patients; a pilot study

Changes in oral microbiota composition (dysbiosis) have long been known to play a key role in the pathogenesis of oral and systemic diseases including respiratory diseases. However, till now, no study has assessed changes in oral microbiota following tuberculosis (TB) infection in humans.

This is the first study of its kind that aimed to investigate oral microbial dysbiosis in newly diagnosed, treatment naïve, TB patients.

Oral swab samples were collected from newly diagnosed TB patients (n = 20) and age, gender and ethnicity matched healthy controls (n = 10). DNA was extracted and microbiota analyzed by sequencing the hypervariable (V3-V4) region of the bacterial 16S rRNA gene using Illumina MiSeq platform. Bioinformatics and statistical analyses were performed using QIIME and R.

Bacterial richness, diversity and community composition were significantly different between TB patients and healthy controls. The two groups also exhibit differential abundance at phylum, class, genus and species levels. LEfSe analysis revealed enrichment (LDA scores (log₁₀) >2, P < 0.05) of Firmicutes (especially Streptococcus) and Actinobacteriota (especially Rothia) in TB patients relative to healthy controls. Gene function prediction analysis showed upregulation of metabolic pathways related to carbohydrates (butanoate, galactose) and fatty acids metabolism, antibiotics biosynthesis, proteosome and immune system signaling.

These observations suggest significant variations in diversity, relative abundance and functional potential of oral microbiota of TB patients compared to healthy controls thereby suggesting potential role of oral bacterial dysbiosis in TB pathogenesis. However, longitudinal studies using powerful metagenomic and transcriptomic approaches are crucial to more fully understand and confrim these findings.