Bacterial topography of the respiratory tract, including pulmonary site-of-disease, in people with active tuberculosis: a case-control study

<underline>Background</underline> : No comprehensive characterization of the respiratory tract (RT) microbiota has been done in people with tuberculosis (TB), a leading global cause of death. <underline>Methods</underline> : 16S rRNA gene sequencing was done on upper RT (URT; oral-washes, naso- and oro-pharyngeal swabs, supraglottic fluid), sputum and lower RT [LRT; bronchoalveolar lavage fluid (BALF) and protected specimen brushings] specimens from HIV-negative people with Xpert MTB/RIF-confirmed TB (cases; n=17) and healthy controls (n=11). In addition to their diseased lobe, cases had their non-diseased lobe sampled. <underline>Results</underline> : The LRT had the lowest α-diversity and β-diversity differed compared to other respiratory compartments. In cases, Mycobacterium relative abundance was highest in the diseased lobe 1.537% (CI 0-3.114), followed by the nasopharynx 0.059% (0.012-0.105), non-diseased lobe 0.054% (0-1.620), oropharynx 0.003% (0-0.010) and sputum 0.002% (0-0.004). Compared to the URT and sputum, cases’ LRTs were Mycobacterium- and Moraxella -enriched ( Erythromicrobium -enriched versus sputum only). In paired comparisons of diseased versus non-diseased lobes in cases, the only differential taxon was Mycobacterium . Amongst non-diseased lobes, those of cases versus controls had reduced α-diversity with Mycoplasma -enrichment and Moraxella- and Klebsiella- depletion. <underline>Conclusion</underline> : Compared to healthy people, those with TB have a less diverse LRT microbiota, characterized by Mycobacterium -enrichment (within the diseased lobe and surprisingly least so in sputum) and depletion of taxa associated with healthy people. In people with TB, most microbial DNA is not mycobacterial within the diseased lobe and even the non-diseased lobes of cases are microbially distinct from controls. These findings provide a foundation for understanding respiratory tract host-microbiome interactions in TB.