One-third of the world’s population is estimated to be latently infected with Mycobacterium tuberculosis . This reservoir of bacteria is largely resistant to antimicrobial treatment that often only targets actively replicating mycobacteria, with current treatment for latent infection revolving around inhibiting the resuscitation event rather than preventing or treating latent infection. As a result, antimicrobials that target latent infection often have little to no activity in vivo. Here we report a method of in vitro analysis of physiologically relevant non-replicating persistence (NRP) utilizing cholesterol as the sole carbon source, alongside hypoxia as a driver of Mycobacterium bovis BCG into the NRP state. Using the minimal cholesterol media NRP assay, we observed an increased state of in vitro resistance to front-line anti-tubercular compounds. However, following a phenotypic screen of an approved-drug library, we identified dapsone as a bactericidal active molecule against cholesterol-dependent NRP M. bovis BCG. Through an overexpression trial of probable antimicrobial target enzymes, we further identified FolP2, a non-functional dihydropteroate synthase homologue, as the likely target of dapsone under cholesterol-NRP due to a significant increase in bacterial resistance when overexpressed. These results highlight the possible reason for little in vivo activity seen for current front-line anti-NRP drugs, and we introduce a new methodology for future drug screening as well as a potential role for dapsone inclusion within the current treatment regime.
Bibliographical note© 2022 The Authors
This is an open-access article distributed under the terms of the Creative Commons Attribution License. This article was made open access via a Publish and Read agreement between the Microbiology Society and the corresponding author’s institution.
Funding: Funding information
J.A.G.C. is grateful to the Academy of Medical Sciences, Global Challenges Research Fund, Birmingham Women’s and Children’s Hospital Charity
Research Foundation and Give A Child Health Fund for their continued support of the Mycobacterial Research Group at Aston University. This research was funded by the Academy of Medical Sciences/the British Heart Foundation/the Government Department of Business, Energy and Industrial
Strategy/Global Challenges Research Fund/the Wellcome Trust Springboard Award [SBF003\1088]. S.E.R.G. is supported with a PhD Studentship
funded by Aston University. A.M. is supported with a PhD Studentship jointly funded by LifETIME CDT (EPSRC and SFI) and Sphere Fluidics. J.H. is
supported by a Venture Innovation Award from the Cystic Fibrosis Trust, UK, VIA Award Number: 098.
- cholesterol metabolism
- Latent tuberculosis infection
- Non-replicating persistence and tuberculosis