Bedaquiline- and clofazimine-resistant Mycobacterium tuberuclosis reference strains available in public collection of mycobacterial strains BCCM/ITM

The global burden of multi-drug tuberculosis (MDR-TB) was estimated  in 2013 at  5.3% of TB cases, including  9% with extensively drug-resistant tuberculosis (XDR-TB)1.  Only 48% of MDR cases were treated successfully, in part due to high toxicity, the long duration of the current regimens, and drug supply interruptions. To overcome these constraints, new TB drugs were deemed essential  and have been  developed, yet their safety and efficacy are being assessed in Phase II and III clinical trials for patients with MDR-TB.

One of these novel drugs is bedaquiline (BDQ), also referred to as Sirturo ®, R207901 or TMC207. BDQ is a diarylquinoline blocking mycobacterial ATP synthesis through the inhibition of ATP synthase,  resulting in strong antimycobacterial activity2,3. In 2012 the U.S.  Food and Drug Administration (FDA) approved BDQ as part of combination therapy to treat adults with MDR-TB when other alternatives are not available4. One year later, in order to avoid uncontrolled use of the drug, WHO published the interim policy guidance for the use of BDQ in treatment of MDR-TB on the basis of Phase II b trial data5. BDQ-resistant Mycobacterium tuberculosis mutants have been described, involving two mechanisms: (1) target-based resistance following mutations in the atpE gene6 , and (2) increased efflux following mutations in the regulatory gene of the mmpL5-mmpS5 efflux pump (Rv0678 gene)7,8.

Clofazimine (Cfz) is an old anti-leprosy drug with demonstrated anti-TB activity that is part of the currently most successful MDR-TB regimen9. The exact mode of action of Cfz remains unknown, yet it shares the Rv0678-driven resistance mechanism with BDQ7,8.

Along with the introduction of these new drugs, comes the need for  standardized drug-susceptibility testing methods and the use of appropriate reference strains.

BCCM/ITM has incorporated the first publically available in vitro selected reference strains for BDQ and Cfz, and is in the process of expanding these numbers, as well as adding reference strains for other recently discovered drugs. These strains were selected from baseline strains susceptible to most of the first-line anti-TB drugs, by growing them on medium containing the respective drugs.

The following strains are now available :


ITM culture number

Original ID




Rv0678 gene

atpE gene

Selected on medium cotaining














Del A 344











MIC= minimal inhibitory concentration determined by the REMA method; WT = wildtype


  1. Multidrug resistant tuberculosis (MDR-TB). 2014 update. WHO. (
  2. Andries K, Verhasselt P, Guillemont , Gohlmann, Neefs J M, Winkler H, Van Gestel J, Timmerman P, Zhu M, Lee E, Williams P, de Chaffoy  D, Huitric E, Hoffner S, Cambau E, Truffot-Pernot C, Lounis N and Jarlier V. 2005.  A diarylquinoline drug active on the ATP synthase of Mycobacterium tuberculosis. Science 307:223-7.
  3. Koul A, Dendouga N, VergauwenK, Molenberghs B, Vranckx L, Willebrords R, Ristic Z, Lill H, Dorange I, Guillement J, Bald D and Andries K. 2007. Diarylquinolines target subunit c of mycobacterial ATP synthase. Nazt Chem Biol. 3:323-324.
  4. Sirturo (bedaquiline) product insert. Silver Spring, MD: Food and Drug Administration (
  5. The use of bedaquiline in the treatment of multidrug-resistant tuberculosis. Interim policy guidance (WHO/HTM/TB/2013.6). Geneva, World Health Organization. 2013.
  6. Huitric E, Verhasselt P, Andries K and Hoffner SE. 2007. In vitro antimycobacterial spectrum of  Diarylquinoline ATP synthase inhibitor. Antimicrob Agents Chemother. 51(11): 4202-4204.
  7. Hartkoorn R C, Uplekar S and Cole S T. 2014. Cross-resistance between clofazimine and bedaquiline through upregulation of MmpL5 in Mycobacterium tuberculosis. Antimicrob Agents Chemother.  58(5): 2979-2981.
  8. Andries K, Villellas C, Coeck N, Thys K, Gevers T, Vranckx L, Lounis N, de Jong BC, Koul A. 2014. Acquired resistance of Mycobacterium tuberculosis to bedaquiline. PLoS One. 10;9(7):e102135.
  9. Van Deun, A., A. Kya Jai Maug, M. A. Halim, P. Kumar Das, M. Ranjan Sarker, P. Daru, and H. L. Rieder. 2010. Short, highly effective, and inexpensive standardized treatment of multidrug-resistant tuberculosis. Am.J.Respir.Crit.Care Med. 182:684-692.
  10. Matsumoto M, Hashizume H, Tomishige T, Kawasaki M, Tsubouchi H, Sasaki H, Shimokawa Y, Komatsu. 2006 OPC-67683, a nitro-dihydro-imidazooxazole derivative with promising action against tuberculosis in vitro and in mice. PLoS Med. 3(11):e466.
  11. Coeck N, Villellas C, Andries K, de Jong BC, Rigouts L. Clofazimine-resistant M. tuberculosis strains in vitro selected: susceptibility to efflux pump inhibitors and cross-resistance to bedaquiline. Poster presented at: 35th Annual Congress of the European Society of Mycobacteriology; 2014 June 29 – July 2; Vienna, Austria.



Date of publication: 
Tuesday, December 16, 2014