Biophysical Society Thematic Meeting - November 16-20, 2015

Biophysics in the Understanding, Diagnosis, and Treatment of Infectious Diseases Poster Abstracts

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.

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