AnethA-ethR-Deficient Mycobacterium bovis BCG Mutant Displays Increased Adherence to Mammalian Cells and Greater PersistenceIn Vivo, Which Correlate with Altered Mycolic Acid Composition

Abstract

ABSTRACTTuberculosis remains a major worldwide epidemic because of its sole etiological agent,Mycobacterium tuberculosis. Ethionamide (ETH) is one of the major antitubercular drugs used to treat infections with multidrug-resistantM. tuberculosisstrains. ETH is a prodrug that requires activation within the mycobacterial cell; its bioactivation involves theethA-ethRlocus, which encodes the monooxygenase EthA, while EthR is a transcriptional regulator that binds to the intergenic promoter region of theethA-ethRlocus. While most studies have focused on the role of EthA-EthR in ETH bioactivation, its physiological role in mycobacteria has remained elusive, although a role in bacterial cell detoxification has been proposed. Moreover, the importance of EthA-EthRin vivohas never been reported on. Here we constructed and characterized an EthA-EthR-deficient mutant ofMycobacterium bovisBCG. Our results indicate that absence of theethA-ethRlocus led to greater persistence ofM. bovisBCG in the mouse model of mycobacterial infection, which correlated with greater adherence to mammalian cells. Furthermore, analysis of cell wall lipid composition by thin-layer chromatography and mass spectrometry revealed differences between theethA-ethRKO mutant and the parental strain in the relative amounts of α- and keto-mycolates. Therefore, we propose here thatM. bovisBCGethA-ethRis involved in the cell wall-bound mycolate profile, which impacts mycobacterial adherence properties andin vivopersistence. This study thus provides some experimental clues to the possible physiological role ofethA-ethRand proposes that this locus is a novel factor involved in the modulation of mycobacterial virulence.