Altered Fatty Acid Metabolism Due to Rifampicin-Resistance Conferring Mutations in the rpoB Gene of Mycobacterium tuberculosis: Mapping the Potential of Pharmaco-metabolomics for Global Health and Personalized Medicine

We investigated the use of gas chromatography mass spectrometry (GC-MS) metabolomics to better characterize rifampicin-resistance by comparing the fatty acid metabolomes of two rpoB mutant Mycobacterium tuberculosis strains (S522L and S531L) to that of a fully susceptible wild-type parent strain. Using the generated GC-MS metabolite data, principal component analysis (PCA) showed a clear differentiation between all three sample groups analyzed. We subsequently identified those metabolites contributing most to the variation in the data using PCA and partial least squares discriminant analysis (PLS-DA). The altered metabolite markers detected in the rifampicin-resistant mutants indicate a decreased synthesis of various 10-methyl branched-chain fatty acids and cell wall lipids, and an increased use of the shorter-chain fatty acids as carbon sources. Furthermore, the rpoB S531L mutant, previously reported to occur in well over 70% of all clinical rifampicin-resistant M. tuberculosis strains, potentially showed a better capacity for using these alternative energy sources, compared to the less frequently detected rpoB S522L mutant. This study is the first of its kind to associate rifampicin resistance, rpoB mutations, and the beta-subunit of RNA polymerase in M. tuberculosis, with an altered fatty acid metabolism, thereby demonstrating the role that pharmaco-metabolomics can play in identifying new markers associated with drug resistance.