Variation in Mycobacterium tuberculosis genotype and molecular phenotype influence clinical phenotype of Pulmonary tuberculosis and Tuberculous Meningitis infection in host

In the present study, we investigated tissue specific colonization and virulence characteristics of two different Mycobacterium tuberculosis (MTB) clinical isolates derived from patients with Pulmonary TB (PTB) and Tuberculous Meningitis (TBM). We retrospectively studied a total of 1458 patients diagnosed with TB between 2003 and 2013. Of these, archived sputum and CSF samples were available for 323 TBM and 157 PTB patients. We selected a total of 10 sputum and CSF isolates from each group for further molecular characterization. Methodologies employed included, Gas chromatographic analyses of Fatty Acid Methyl Esters (GC-FAME) followed by MTB genotyping to assess strain diversity. We further assessed the molecular phenotype of each strain through in-vitro cytokine assays & murine MTB model. Our comparative genomics data illustrated two diverse genotypes belonging to H37RV (PTB) and CCDC5079 linkage (TBM), highlighting major variation in membrane protein composition and enzymes that make different mycolic acids. The differential cytokine response by both the strains & GC-FAME analysis further corroborated this variation in membrane composition. This was in agreement with KasIII enzyme, LppA and desaturase related variation in protein. Both MTB strains in mice showed diverse pathogenesis with CCDC5079 infected mice exhibiting higher dissemination to brain compared to the H37RV strain which developed progressive pulmonary disease. These observations suggest that variation in the MTB membrane composition could play an important role in differential colonization of these strains. The study warrants further investigation of membrane proteins with respect to blood brain barrier invasion and pathogenesis.