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Biophysics in the Understanding, Diagnosis, and Treatment of Infectious Diseases Poster Abstracts
91
20-POS
Board 20
Bedaquiline, Q203, and Clofazimine: Novel Insights into Effects on M. Tuberculosis
Respiration
Dirk Lamprecht
1
, Peter Finin
1,2
, Bridgette Cumming
1
, Adrie Steyn
1,3
.
1
K-RITH, Durban, KwaZulu-Natal, South Africa,
2
University of Michigan, Ann Arbor, MI,
USA,
3
University of Alabama at Birmingham, Birmingham, AL, USA.
Understanding how different conditions and antibiotic compounds affect
Mycobacterium
tuberculosis
(
Mtb
) energy production through oxidative phosphorylation (OXPHOS) and carbon
catabolism has substantial implications for drug discovery and optimization. We have developed
a bioenergetic assay by existing adapting extracellular flux (XF) technology, previously used
primarily to study eukaryotes, to non-invasively provide real-time data on
Mtb
’s O
2
consumption
rate (OCR, a measure of OXPHOS) and extracellular acidification rate (ECAR, a measure of
carbon catabolism). This fully integrated multi-well technology can now be used to rapidly
investigate, under relevant physiological conditions, compounds that target
Mtb
energy
production.
We have made the surprising discovered that the two new anti-mycobacterial drugs bedaquiline
(BDQ) and Q203, respectively targeting Complex V and Complex III of the mycobacterial
electron transport chain (ETC), cause an increase in
Mtb
’s OCR up to approximately four-fold
above that of untreated cells. The increase in OCR is not transient and is maintained for at least
16 hours after drug addition. The increase in OCR is even more pronounced at lower O
2
tensions,
similar to those found in a host macrophage or granuloma. This effect is not observed for
clofazimine (CFZ), another mycobacterial ETC targeting drug. Also, the increase in OCR is not
associated with the production of ATP and is not due to classic uncoupling of the mycobacterial
ETC. Furthermore, there is also a sustained increase in ECAR after the addition of BDQ and
Q203, an indication that OXPHOS is not meeting energy requirements. Together, the OCR and
ECAR results suggest that O
2
consumption, while stimulated, is no longer effectively coupled to
energy production.
In sum, we have developed an innovative method to explore the effects of new compounds that
target
Mtb
bioenergetics.