Multidrug-resistant Tuberculosis

From Tuberculosis Wiki

Multidrug-resistant tuberculosis (MDR-TB), is a type of drug-resistant tuberculosis that has developed resistance to at least the two most common and effective drugs used in TB treatment: isoniazid and rifampin.[1] MDR-TB first emerged as a global health problem in the 1990s, with treatments depending on the use of toxic injectable drugs like kanamycin and capreomycin.[2] Since 2018, the World Health Organization (WHO) has recommended all-oral regimens for treatment of MDR-TB, making use of bedaquiline, and phasing out injectable drug-regimens.[3][2]

Prevalence[edit | edit source]

In 2022, around 410,000 people developed multidrug-resistant or rifampin-resistant tuberculosis (RR-TB), about 3.3% of new cases and 17% of people who had been previously treated.[3] Three countries accounted for 42% of all MDR/RR-TB: India, the Philippines, and the Russian Federation. Only about 43% of the estimated number of people with MDR/RR-TB were diagnosed and started on treatment.[3]

Testing[edit | edit source]

Diagnosing drug-resistant tuberculosis relies on drug susceptibility testing (DST).[4] DSTs can be separated into two broad categories: tests that observe growth or metabolic inhibition in a medium containing drugs used to treat TB (phenotypic tests), and tests that detect genes associated with particular forms of drug-resistance (molecular tests).[5] Rapid molecular tests for drug-resistant TB or nucleic acid amplification tests (NAATs), such as Xpert MTB/XDR and MTB/RIF cartridges are molecular tests that have the ability to diagnose MDR-TB within hours, but when not available due to low sample size, high prices, or other common barriers, phenotypic testing has to be used, which can take as long as two to three months to confirm diagnosis with, prolonging the time before a person can be given appropriate treatment.[4] Since molecular tests can only detect resistance when it occurs through pre-programmed mutations, culture based phenotypic testing is still recommended after a person has received a rapid molecular test, to further personalize treatment and catch drug-resistance that has occurred through unusual mutations, where possible.[6]

Treatment[edit | edit source]

Treating multidrug-resistant tuberculosis requires the use of second-line drugs. Treatments can sometimes involve daily injections for six months, and up to 14,000 individual pills,[7] with side effects including depression, hearing loss, and joint pain, as well as vomiting and reduced appetites, which can have the additional affect of worsening the disease.[8] In December 2022, WHO recommended, shorter all oral regimens for treatment of MDR-TB, making use of newer drugs like pretomanid and bedaquiline.[9] MDR-TB treatment regimens are often extremely expensive, which combined with the adverse side effects of treatment contributes to the fact that in 2022 about 160,000 people died of MDR/RR-TB.[3] Though success rates continue to increase, in 2021 only 71% of people with MDR/RR-TB who received treatment were successfully cured.[10]

References[edit | edit source]

  1. ^ "Tuberculosis: Multidrug-resistant tuberculosis (MDR-TB)". WHO. World Health Organization. 16 January 2018. Retrieved 10 February 2024.
  2. ^ a b Viney, Kerri; Nguyen Nhat, Linh; Gegia, Medea; Zignol, Matteo; Glaziou, Philippe; Ismail, Nazir; Kasaeva, Tereza; Mirzayev, Fuad (April 2021). "New definitions of pre-extensively and extensively drug-resistant tuberculosis: update from the World Health Organization". European Respiratory Society. 57. doi:10.1183/13993003.00361-2021. PMID 33833074.
  3. ^ a b c d Global Tuberculosis Report 2023 (Report). World Health Organization. 2023. ISBN 9789240083851.
  4. ^ a b Jang JG, Chung JH (October 2020). "Diagnosis and treatment of multidrug-resistant tuberculosis". Yeungnam Univ J Med. 37 (4): 277–285. doi:10.12701/yujm.2020.00626. PMC 7606956. PMID 32883054.
  5. ^ Kim SJ (March 2005). "Drug-susceptibility testing in tuberculosis: methods and reliability of results". Eur Respir J. 25 (3): 564–9. doi:10.1183/09031936.05.00111304. PMID 15738303.
  6. ^ "Tuberculosis Molecular Diagnostic Testing Information for Healthcare Workers and Laboratorians". Rhode Island Department of Health. 2009. Retrieved 4 March 2024.
  7. ^ "Inadequate Treatment". TB Alliance. Retrieved 23 February 2024.
  8. ^ Madhav, Bhumika; Iyer, Aparna; Jayalakshmi, T.K. (2015). "Side effect profile of 2nd line drugs in multi drug resistant (MDR) and extensively drug resistant (XDR) tuberculosis". European Respiratory Journal. 46. doi:10.1183/13993003.congress-2015.PA2708.
  9. ^ "WHO announces landmark changes in treatment of drug-resistant tuberculosis". World Health Organization. 15 December 2022. Retrieved 1 March 2024.
  10. ^ "DR-TB Treatment Success Rate". TB DIAH. Retrieved 7 March 2024.