Multidrug-resistant tuberculosis is a serious threat to global public health.
Mona Drage og Thomas Jürgens
Ole Morten Melgård
Resistant tuberculosis means that the tuberculosis bacteria are resistant to the standard tuberculosis medications. This makes resistant tuberculosis more difficult to treat. One has to take several different medications over a longer period – normally up to two years.
Resistant tuberculosis is often referred to as MDR-TB (multidrug-resistant tuberculosis) or XDR-TB (extensively drug-resistant tuberculosis).
In MDR-TB, the tuberculosis bacteria are resistant to the two main first-line medications, isoniazid and rifampicin.
In XDR-TB, in addition to resistance to isoniazid and rifampicin, there is resistance to two of the main medications that are used to treat MDR-TB (at least one of the fluoroquinolones as well as at least one of the following three medications: capreomycin, kanamycin, or amikacin).
Tuberculosis with bacteria that are resistant to both isoniazid and rifampicin (the two main first-line medications for the treatment of tuberculosis) and possibly also other medications.
Tuberculosis with bacteria that are resistant to the two first-line medications (rifampicin and isoniazid) as well as at least one fluoroquinolone and at least one of the following three medications: capreomycin, kanamycin, or amikacin.
Patients with XDR-TB can still be treated, but some of the medications used have serious side effects, and the treatment outcomes for this patient population are poor.
Another challenge is that XDR-TB drugs are not available everywhere. This can result in the patients being “non-treatable”.
Resistant tuberculosis developed because:
The combination of medications that patients have taken were formulated incorrectly.
Patients have received insufficient dosage of medications.
Patients have not taken all the doses of their medications.
Patients have had long interruptions in treatment.
There has been poor quality control in the production of the medications.
There has been poor supervision or management of the treatment.
A patient has been infected with bacteria that were already resistant.
A person has received treatment in an incompetent health care setting that fails to provide a reasonable standard of tuberculosis care.
Undiagnosed and untreated cases
The World Health Organization (WHO) estimates that 465 000 people developed MDR tuberculosis in 2019. However, only around 206 000 of these were diagnosed,and 177 000 put on treatment. Out of these, 56% was cured.
India, China, and Russia have the most cases of MDR-TB in the world, but MDR-TB has also become a big problem in the former Soviet states as well as parts of Eastern Europe. It is essential to increase access to diagnosis and treatment in order to significantly lessen the gap between those who have MDR-TB and those that actually receive treatment for it.
Treatment of resistant tuberculosis
The treatment of patients with MDR- and XDR-TB (see fact box) is very resource intensive and difficult, both for the person who is sick and for the health care services. The treatment takes up to two years, and the necessary medication can cost up to 200 times more than the standard treatment.
The effort to combat resistant tuberculosis is made extra challenging by the fact that the majority of cases are found in low- and middle-income countries where the capacity of the health care system to handle cases of MDR- or XDR-TB is extremely limited. Many patients are also reluctant to carry out the treatment because of the strong and unpleasant side effects of the medications.
Prevention of resistant tuberculosis
The most important measure to take to prevent the development of resistant tuberculosis bacteria is to ensure that patients are closely followed when they are treated for “ordinary” tuberculosis. The treatment of resistant tuberculosis demands close monitoring over a long period of time, and it is essential that the patient complete the treatment regimen. MDR- and XDR-TB are often a result of the patient, for various reasons, stopping the treatment too early. Therefore, patients need to be carefully observed during the treatment period.
The development of resistant tuberculosis is still not an issue in Norway because of the good quality control over medicines and treatment.
New drugs for tuberculosis treatment
Two new drugs, bedaquiline (bedakvilin in Norwegian) and delamanid, are now being introduced. They have been specially developed to treat resistant tuberculosis. The cost of these medications is high, and the availability, for the time being, is very limited.
Bedaquiline and delamanid makes it possible to shorten the demanding regimen for treating drug-resistant tuberculosis. It is vitally important that these potent new drugs are carefully managed in order to prevent future drug resistance.