Mutation in alkylhydroperoxidase D gene dramatically decreases persistence of Mycobacterium bovis   bacillus calmette-guerin in infected macrophage

Background and Objectives: Mycobacterium tuberculosis is the leading cause of death from a single bacterial species in the world and is subjected to a highly oxidative environment in its host macrophage and consequently has evolved protective mechanisms against reactive oxygen and nitrogen intermediates. Alkyl hydroperoxidase D (AhpD) is a molecule from these mycobacterial defense systems that has a dual function. It not only works with Alkyl hydroperoxidase C (AhpC) in mycobacterial defense system against oxidative stress but also has a role in oxidation/reduction of succinyltransferase B (SucB), dihydrolipoamide dehydrogenase (LPD) and AhpC. The present study was undertaken to find out the effects of inactivation of ahpD gene in the intra-macrophage persistence of resulted BCG mutant.
Materials and Methods: We did allelic exchange mutagenesis in Mycobacterium bovis BCG and evaluate the effects of this mutagenesis in intracellular persistence of wild type BCG strains and ahpD mutant ones by comparing colony forming units (CFU) in infected macrophage.
Results: Our findings showed that after producing allelic exchange mutagenesis in ahpD gene of M.bovis BCG a sever decrease in the CFU′s of ahpD mutant BCG strains has been observed and intracellular persistence of ahpD mutant BCG strains decreased significantly.
Conclusion: Mutagenesis in ahpD gene will cause significant decrease in intracellular survival of ahpD mutant strains than wild type M.bovis BCG strains and could leads to an inefficiency in pyruvate dehydrogenase pathway and could also impair impairs mycobacterial defense system against oxidative and nitrosative stress.