News

EXTENSIVELY DRUG-RESISTANT TB (XDR TB)

Related Topics: Science & Technology, Anti Microbial Resistance

 

News

  • Recently, the United States Food and Drug Administration have approved a three-drug regimen against the most lethal form of multi-drug-resistant tuberculosis, known as the XDR (extensively drug-resistant) strain.
  • The treatment involves pretomanid tablets in combination with bedaquiline and linezolid and has an efficacy rate of 90 per cent.
  • This three-drug regimen is collectively known as BPaL regimen and it can cure highly drug-resistant strains of tuberculosis by drastically shortening treatment period.

 

Significance

  • There are 1,14,237 MDR-TB patients globally, of which more than 8,000 are XDR-TB, according to 2018 WHO TB update.
  • The success rate of treatment for XDR-TB in India is merely 23 per cent.
  • The new drug regimen is important for countries like India, which has the second-highest burden to XDR-TB patients in the world, after

 

What is XDR TB?

  • It is a form of TB which is resistant to at least four of the core anti-TB drugs.
  • XDR-TB involves resistance to the two most powerful anti-TB drugs, isoniazid and rifampicin, also known as multidrug-resistance (MDR-TB).
  • In addition, it involves resistance to any of the fluoroquinolones (such as levofloxacin or moxifloxacin) and to at least one of the three injectable second-line drugs (amikacin, capreomycin or kanamycin).

 

How XDR TB is different from MDR TB?

  • When TB infection becomes resistant to the first line of treatment — isoniazid and rifampicin, it is called MDR-TB.
  • When the infection becomes resistant even to the second-line treatment, it is called XDR-TB.

 

How do people get XDR-TB?

  • People may get XDR-TB in one of two ways.
  • It may develop in a patient who is receiving treatment for active TB, when anti-TB drugs are misused or mismanaged, and is usually a sign of inadequate clinical care or drug management.
  • The second way that people can develop XDR-TB is by becoming infected from a patient who is already ill with the condition. Patients with TB of the lungs can spread the disease by coughing, sneezing, or simply talking.

 

Can XDR-TB be cured or treated?

  • XDR-TB patients can be cured, but with the current drugs available, the likelihood of success is much smaller than in patients with ordinary TB or even MDR-TB.
  • Cure depends on the extent of the drug resistance, the severity of the disease and whether the patient’s immune system is compromised.

 

 XDR TB and HIV

  • People living with HIV are at greater risk of developing TB – as well as XDR-TB – than people without HIV, because of their weakened immunity.
  • In places where XDR-TB strains circulate more frequently, people with HIV are therefore more likely to be infected with XDR-TB than elsewhere.
  • To date, in most of the places with high rates of HIV infection, XDR-TB has not been widespread.

 

Way Forward

  • Global TB control requires a sustained commitment by scientific, political and financial authorities.
  • One of the first priorities should be given to effectively diagnose XDR-TB in clinical practice by increasing the laboratory capacity
  • New research in the areas involving application of molecular biology in the field of epidemiology could help in better understanding of the mechanisms leading to drug resistance, development of newer diagnostic tools and effective drugs to control DR-TB.
  • The effective management of XDR-TB depends on judicious prescription of second line drugs (SLDs) to reduce morbidity and mortality and transmission based on the current scenario.
  • TB control programmes should emphasize on policies focusing on the effective use of first-line drugs in every new patient so as to prevent the emergence of MDR-TB, XDR-TB and XXDR-TB or TDR-TB.

 

[Sources: WHO, Indian Journal of Medical Research, Down To Earth, Indian Express]

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