Bedaquiline Resistance – Causes, Diagnosis & Treatment
Bedaquiline resistance refers to the reduced effectiveness of the antibiotic bedaquiline against tuberculosis bacteria, posing a serious challenge to MDR-TB treatment.
Things worth knowing about "Bedaquiline resistance"
Bedaquiline resistance refers to the reduced effectiveness of the antibiotic bedaquiline against tuberculosis bacteria, posing a serious challenge to MDR-TB treatment.
What is Bedaquiline Resistance?
Bedaquiline resistance refers to the ability of Mycobacterium tuberculosis – the bacterium causing tuberculosis (TB) – to survive exposure to the antibiotic bedaquiline. Bedaquiline is one of the few recently approved medications specifically indicated for the treatment of multidrug-resistant tuberculosis (MDR-TB) and extensively drug-resistant tuberculosis (XDR-TB). The emergence of resistance against this drug therefore poses a critical threat to global tuberculosis control efforts.
Causes of Bedaquiline Resistance
Bedaquiline resistance in M. tuberculosis arises through genetic mutations. The key mechanisms include:
- Mutations in the atpE gene: The atpE gene encodes a subunit of the mycobacterial ATP synthase, which is the direct molecular target of bedaquiline. Point mutations in this gene reduce the binding affinity of the drug to its target.
- Upregulation of the MmpL5 efflux pump system: Mutations in the regulatory gene Rv0678 lead to increased expression of efflux pumps that actively transport bedaquiline out of the bacterial cell, reducing intracellular drug concentrations.
- Cross-resistance: Resistance mechanisms against bedaquiline can simultaneously confer resistance to other important reserve drugs such as clofazimine, further limiting available treatment options.
- Acquired resistance due to inadequate therapy: Incomplete or non-guideline-compliant treatment favours the selection of resistant bacterial strains.
Clinical Significance for Tuberculosis Treatment
Bedaquiline has been classified by the World Health Organization (WHO) as a core Group B drug for the treatment of MDR-TB. It inhibits the mycobacterial ATP synthase, an enzyme essential for the energy metabolism of the bacterium. Because bedaquiline has a completely novel mechanism of action, it remained active against strains resistant to classical TB drugs for a significant period. The growing prevalence of bedaquiline resistance now threatens this crucial therapeutic advantage.
Diagnosis of Bedaquiline Resistance
Detection of bedaquiline resistance requires specialised laboratory investigations:
- Phenotypic drug susceptibility testing (DST): The isolated bacterial strain is tested for growth in the presence of bedaquiline. According to WHO recommendations, the critical concentration is 1.0 µg/ml in liquid culture medium (MGIT system).
- Molecular genetic testing: DNA sequencing of the bacterial genome can directly identify known resistance mutations, particularly in the atpE and Rv0678 genes.
- Whole-genome sequencing (WGS): Comprehensive genomic analysis allows detection of all potential resistance mutations and is increasingly recognised as the gold standard in specialised reference laboratories.
Treatment Options in Cases of Bedaquiline Resistance
When bedaquiline resistance is confirmed, treatment options become extremely limited. Management should be carried out exclusively in specialised centres experienced in drug-resistant tuberculosis. Possible approaches include:
- Use of other reserve drugs such as linezolid, delamanid, or pretomanid, provided they remain effective.
- Individualised treatment regimens based on the complete resistance profile of the infecting strain.
- Consultation with WHO experts and national tuberculosis programmes for complex cases.
Prevention and Global Significance
Preventing the emergence and spread of bedaquiline resistance is of paramount global importance. Key preventive measures include strict adherence to standardised treatment protocols, regular resistance testing, and close monitoring throughout therapy. The WHO emphasises that bedaquiline should only be used as part of a complete, guideline-compliant treatment regimen to minimise the selection of resistant strains.
References
- World Health Organization (WHO): WHO Consolidated Guidelines on Tuberculosis, Module 4: Treatment – Drug-Resistant Tuberculosis Treatment. Geneva: WHO, 2022.
- Sutherland HS et al.: Bedaquiline and Bedaquiline Resistance: Mechanisms, Epidemiology and Clinical Management. Antimicrobial Agents and Chemotherapy, 2023.
- Conradie F et al.: Treatment of Highly Drug-Resistant Pulmonary Tuberculosis. New England Journal of Medicine, 2020; 382:893–902.
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