Respiratory microbiome and its susceptibility to Mycobacterium tuberculosis infection

Respiratory throat acts as an ecological niche for various microorganisms. These
\nmicrobial communities play important roles in the maintenance of human health.
\nAlthough the interest in microbial composition of microbiota in respiratory tracts has
\nrecently been increased, the possible relationship between the composition and abundance
\nof microbiota in the ecological niche of human throat with Mycobacterium tuberculosis
\ninfection are poorly understood. This study was aimed to investigate the composition of
\nthroat microbiota in pulmonary tuberculosis patients in comparison to healthy TST
\n(Tuberculin Skin Test) positive and TST negative subjects. The microbiota of the throat
\nwas fully characterized by 16s rRNA Metagenomics sequencing. The study revealed that
\naltogether, there were 7 phyla and 35 genera in the throat of enrolled subjects. The main
\nphyla were Firmicutes, Bacteriodetes, Proteobacteria and Actinobacteria. The
\npredominant communities of genera were Streptococcus, Staphylococcus,
\nCapnocytophaga, Rothia and Enterococcus. The microbiota composition of TB patients
\nand asymptomatic TST positive subjects were more heterogeneous as compared to the
\nthroat microbiota of healthy TST negative subjects. Streptococcus was found to be
\nsignificantly abundant in throat of healthy compared to asymptomatic TST positive
\nsubjects and TB patients. In TB patients, Bifidobacterium, Bulleidia, Butyrivibrio,
\nChryseobacterium and Pediococcus were among the genera present abundantly in their
\nthroats compared to TST negative. At genus level, Lactobacillus salivarius was
\nsignificantly higher in the throat of TB patients compared to TST positive individuals.
\nStreptococcus sobrinus and Bulleidia moorei were also significantly higher in TB patients
\nwhen compared with those in the throats of TST negative individuals. Alpha diversity and
\nbeta diversity analysis were also performed in this study. No significant difference was
\nobserved between the three groups in alpha indices indicating the equally diverse
\nmicrobiota in terms of richness and evenness of the species. In beta diversity analysis, the
\nunweighted unifrac of TB patients and TST negative groups were statistically higher
\ncompared to TST positive group, indicating the higher presence of particular cluster or
\nspecies in their throats. Weighted unifrac of TST positive was statistically higher than that
\nof TB patients and TST negative groups which indicates more distantly related organisms
\ninhabiting the communities. This investigation was consistent with earlier studies and our
\nfindings indicate that throat microbiota may play a role in the susceptibility or resistance
\nto Mycobacterium tuberculosis infection. The relevance of these microbiota may need to
\nbe taken into consideration to improve methods of control of TB disease in the future.