Rifamycin action on RNA polymerase in antibiotic-tolerant Mycobacterium tuberculosis results in differentially detectable populations

Proc Natl Acad Sci U S A. 2017 Jun 13;114(24):E4832-E4840. doi: 10.1073/pnas.1705385114. Epub 2017 May 30.


Mycobacterium tuberculosis (Mtb) encounters stresses during the pathogenesis and treatment of tuberculosis (TB) that can suppress replication of the bacteria and render them phenotypically tolerant to most available drugs. Where studied, the majority of Mtb in the sputum of most untreated subjects with active TB have been found to be nonreplicating by the criterion that they do not grow as colony-forming units (cfus) when plated on agar. However, these cells are viable because they grow when diluted in liquid media. A method for generating such "differentially detectable" (DD) Mtb in vitro would aid studies of the biology and drug susceptibility of this population, but lack of independent confirmation of reported methods has contributed to skepticism about their existence. Here, we identified confounding artifacts that, when avoided, allowed development of a reliable method of producing cultures of ≥90% DD Mtb in starved cells. We then characterized several drugs according to whether they contribute to the generation of DD Mtb or kill them. Of the agents tested, rifamycins led to DD Mtb generation, an effect lacking in a rifampin-resistant strain with a mutation in rpoB, which encodes the canonical rifampin target, the β subunit of RNA polymerase. In contrast, thioridazine did not generate DD Mtb from starved cells but killed those generated by rifampin.

Keywords: Mycobacterium tuberculosis; differentially detectable; phenotypic tolerance; rifampin; thioridazine.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Antibiotics, Antitubercular / pharmacology*
  • Antitubercular Agents / pharmacology
  • Bacterial Proteins / antagonists & inhibitors*
  • Bacterial Proteins / genetics
  • DNA-Directed RNA Polymerases / antagonists & inhibitors*
  • DNA-Directed RNA Polymerases / genetics
  • Drug Resistance, Bacterial / genetics
  • Humans
  • Isoniazid / pharmacology
  • Mutation
  • Mycobacterium tuberculosis / drug effects*
  • Mycobacterium tuberculosis / enzymology*
  • Mycobacterium tuberculosis / genetics
  • Rifamycins / pharmacology*
  • Thioridazine / pharmacology
  • Tuberculosis / drug therapy
  • Tuberculosis / microbiology


  • Antibiotics, Antitubercular
  • Antitubercular Agents
  • Bacterial Proteins
  • Rifamycins
  • rpoB protein, Mycobacterium tuberculosis
  • DNA-Directed RNA Polymerases
  • RNA polymerase beta subunit
  • Thioridazine
  • Isoniazid