What is drug resistant TB?
A person has drug resistant TB if the TB bacteria that the person is infected with, will not respond to, which means that they are resistant to, at least one of the main TB drugs.
Drug susceptible TB is the opposite. If someone is infected with TB bacteria that are fully susceptible, it means that all of the TB drugs will be effective so long as they are taken properly. It still means that several drugs need to be taken together to provide effective TB treatment.
How do you find out which drugs can be used to treat it?
Drug susceptibility testing is how you find out which drugs will be effective at treating drug resistant TB.
Is it possible to cure drug resistant TB?
It is more difficult to cure TB which is drug resistant than TB which is fully susceptible, but it is still possible.
How do you get it?
There are two ways that people get it.
- Firstly, people get acquired drug resistant TB when their TB treatment is inadequate. This can be for a number of reasons, including the fact that patients fail to keep to proper TB treatment regimens. It can also be that the wrong TB drugs are prescribed, or sub standard TB drugs are used for treatment.
- Secondly, transmitted or primary drug resistant TB, results from the direct transmission of drug resistant TB from one person to another. The occurrence and prevention of primary drug resistant TB has largely been neglected during the development of global programs to end TB.
New tools have enabled researchers to investigate this further. They have found that primary resistance plays a much greater role than previously thought.1"Report warns of rise in drug-resistant tuberculosis", 2017, http://www.cidrap.umn.edu/news-perspective/2017/03/report-warns-rise-drug-resistant-tuberculosis
Our best estimates are that globally, at least 75% to 80% is now primarily transmitted, as opposed to primarily acquired during treatment. D Dowdy
So simply doing a better job of treating drug susceptible TB is no longer sufficient for controlling drug resistance. To control it, it is necessary to specifically diagnose and treat it.
What are the main types of drug resistant TB?
MDR TB is the name given to TB when the bacteria that are causing it are resistant to at least isoniazid and rifampicin, two of the most effective TB drugs.
XDR TB is defined as strains resistant to at least rifampicin and isoniazid. This is in addition to strains being resistant to one of the fluoroquinolones, as well as resistant to at least one of the second line injectable TB drugs amikacin, kanamycin or capreomycin.2“Extensively drug-resistant tuberculosis (XDR-TB): recommendations for prevention and control”, Weekly epidemiological record, WHO, 2006, www.who.int/
MDR TB and XDR TB do not respond to the standard six months of TB treatment with “first line” anti TB drugs. Treatment for them can often take two years or more and requires treatment with other drugs that are less potent, more toxic and much more expensive. However, there are now starting to be some shorter regimens for treatment, based on the Bangladesh regimen.
What is RR-TB?
RR-TB is Rifampicin resistant TB. Rifampicin resistant TB requires treatment with second line drugs. Statistically RR-TB includes MDR-TB which is resistant to both rifampicin and isoniazid.
What other types are there?
Another type variously referred to as totally drug resistant TB, XXDR-TB or TDR TB has also now been detected.3Velayati, Ali “Emergence of New Forms of Totally Drug Resistant Tuberculosis Bacilli”, Chest, Vol 136, August 2009, no. 2 420-425
http://www.ncbi.nlm.nih.gov/pubmed/ 4Migliori, G “125 years after Robert Koch’s discovery of the tubercle bacillus: the new XDR-TB threat. Is “science” enough to tackle the epidemic?”, European Respiratory Journal, March 1 2007
What are the statistics for rifampicin resistant TB & MDR TB?
Globally, there were an estimated 465,000 incident cases of rifampicin resistant TB in 2019. 78% are estimated to have had multidrug resistant TB.
By country India had 27%, China 14%, and the Russian Federation 8%.
In 2019 there were an estimated 182,000 deaths from MDR/RR-TB.
High burden MDR TB countries
The 30 “high burden” MDR TB countries are:
Angola, Azerbaijan, Bangladesh, Belarus, China, DPR Korea, DR Congo, Ethiopia, India, Indonesia, Kazakhstan, Kenya, Kyrgyzstan, Mozambique, Myanmar, Nigeria, Pakistan, Papua New Guinea, Peru, Philippines, Republic of Moldova, Russian Federation, Somalia, South Africa, Tajikistan, Thailand, Ukraine, Uzbekistan, Viet Nam, Zimbabwe.
There is more about high burden TB countries &
This page was last updated in November 2020.
Author Annabel Kanabus
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