Bacterial and host determinants of cough aerosol culture positivity in patients with drug-resistant versus drug-susceptible tuberculosis

Nat Med. 2020 Sep;26(9):1435-1443. doi: 10.1038/s41591-020-0940-2. Epub 2020 Jun 29.

Abstract

A burgeoning epidemic of drug-resistant tuberculosis (TB) threatens to derail global control efforts. Although the mechanisms remain poorly clarified, drug-resistant strains are widely believed to be less infectious than drug-susceptible strains. Consequently, we hypothesized that lower proportions of patients with drug-resistant TB would have culturable Mycobacterium tuberculosis from respirable, cough-generated aerosols compared to patients with drug-susceptible TB, and that multiple factors, including mycobacterial genomic variation, would predict culturable cough aerosol production. We enumerated the colony forming units in aerosols (≤10 µm) from 452 patients with TB (227 with drug resistance), compared clinical characteristics, and performed mycobacterial whole-genome sequencing, dormancy phenotyping and drug-susceptibility analyses on M. tuberculosis from sputum. After considering treatment duration, we found that almost half of the patients with drug-resistant TB were cough aerosol culture-positive. Surprisingly, neither mycobacterial genomic variants, lineage, nor dormancy status predicted cough aerosol culture positivity. However, mycobacterial sputum bacillary load and clinical characteristics, including a lower symptom score and stronger cough, were strongly predictive, thereby supporting targeted transmission-limiting interventions. Effective treatment largely abrogated cough aerosol culture positivity; however, this was not always rapid. These data question current paradigms, inform public health strategies and suggest the need to redirect TB transmission-associated research efforts toward host-pathogen interactions.

Publication types

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

MeSH terms

  • Adult
  • Aerosols / analysis*
  • Antitubercular Agents / therapeutic use*
  • Cough / microbiology*
  • Female
  • Humans
  • Male
  • Middle Aged
  • Mycobacterium tuberculosis / drug effects
  • Sputum / microbiology
  • Tuberculosis, Multidrug-Resistant / diagnostic imaging
  • Tuberculosis, Multidrug-Resistant / drug therapy*
  • Tuberculosis, Multidrug-Resistant / transmission
  • Tuberculosis, Pulmonary / diagnostic imaging
  • Tuberculosis, Pulmonary / drug therapy*
  • Tuberculosis, Pulmonary / transmission

Substances

  • Aerosols
  • Antitubercular Agents