# Viable but Nonculturable Mtb

> **NIH NIH U19** · WEILL MEDICAL COLL OF CORNELL UNIV · 2020 · $947,618

## Abstract

Tuberculosis (TB) takes longer to cure than almost any other bacterial infection. Subpopulations of
Mycobacterium tuberculosis (Mtb) become phenotypically drug-tolerant in association with host-imposed
stresses that put Mtb into a slowly-replicating or non-replicating state (here called NR for simplicity). We
hypothesize that NR Mtb represent a major population of the "persisters" that survive the first months of
chemotherapy. One subset of NR Mtb is termed "viable but nonculturable" (VBNC) because they elude
detection as colony forming units (CFU) on agar. The nonculturability of VBNC Mtb has left us with almost no
knowledge of their essential genes, metabolic pathways or susceptibilities to specific drugs and drug
candidates. We have now improved a limiting dilution assay for VBNC Mtb and used it to confirm that an
average of 87% of the viable Mtb detected in sputum from 33% of the untreated TB patients studied were
VBNC forms missed both by CFU assays and by liquid culture in the BACTEC MGIT assay. Further, we
developed a reproducible way to generate VBNC Mtb in vitro by prolonged starvation in axenic culture. In
close collaboration with Project 5 and the Clinical Core, we will further improve and apply the resuscitation
assay to characterize VBNC Mtb by chemical genomics in vitro, by genetics in the mouse, and by their
presence in sputum from patients before and after standard therapy. We will deliver: compounds that
eradicate VBNC Mtb in vitro and identification of the targets of these compounds; a mouse model where the
efficacy of such inhibitors can be tested in vivo; and an assay that can be used in future clinical trials to
complement the standard early bactericidal activity test on sputum so as to identify drugs that impact VBNC
Mtb in the human host.

## Key facts

- **NIH application ID:** 10057813
- **Project number:** 5U19AI111143-07
- **Recipient organization:** WEILL MEDICAL COLL OF CORNELL UNIV
- **Principal Investigator:** Michael S Glickman
- **Activity code:** U19 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2020
- **Award amount:** $947,618
- **Award type:** 5
- **Project period:** 2014-07-01 → 2021-06-30

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10057813

## Citation

> US National Institutes of Health, RePORTER application 10057813, Viable but Nonculturable Mtb (5U19AI111143-07). Retrieved via AI Analytics 2026-05-28 from https://api.ai-analytics.org/grant/nih/10057813. Licensed CC0.

---

*[NIH grants dataset](/datasets/nih-grants) · CC0 1.0*