MDR-TB takes longer to treat with second-line drugs (i.e., amikacin, kanamycin, or capreomycin), which are more expensive and have more side-effects.

The World Health Organization (WHO) defines XDR-TB as MDR-TB that is resistant to at least one fluoroquinolone and a second-line injectable drug (amikacin, capreomycin, or kanamycin).

It is therefore vital that TB control be managed properly and new tools developed to prevent, treat and diagnose the disease.

[4] Symptoms of XDR-TB are no different from ordinary or drug-susceptible TB: a cough with thick, cloudy mucus (or sputum), sometimes with blood, for more than two weeks; fever, chills, and night sweats; fatigue and muscle weakness; weight loss; and in some cases shortness of breath and chest pain.

The immune system "walls off" the TB bacilli which, protected by a thick waxy coat, can lie dormant for years.

The risk of becoming infected increases with the longer the time that a previously uninfected person spends in the same room as the infectious case.

The risk of spread increases where there is a high concentration of TB bacteria, such as can occur in closed environments like overcrowded houses, hospitals or prisons.

Some studies have found an in-house assay that could rapidly detect resistance to drugs involved in the definition of XDR-TB directly from smear-positive specimens.

A recent study found that a research technique known as direct nitrate reductase assay (D-NRA) showed efficient accuracy for the rapid and simultaneous detection of resistance to isoniazid (INH), rifampicin (RIF), kanamycin (KAN) and ofloxacin (OFL).

At the same time the study mentioned how D-NRA is a low-cost technology, easy to set up in clinical laboratories and suitable to be used for DST of M. tuberculosis in all smear-positive samples.

[13] These emphasize providing proper diagnosis and treatment to all TB patients, including those with drug-resistant TB; assuring regular, timely supplies of all anti-TB drugs; proper management of anti-TB drugs and providing support to patients to maximize adherence to prescribed regimens; caring for XDR-TB cases in a centre with proper ventilation, and minimizing contact with other patients, particularly those with HIV, especially in the early stages before treatment has had a chance to reduce the infectiousness.

Second-line drugs are more toxic than the standard anti-TB regimen and can cause a range of serious side-effects including hepatitis, depression, hallucinations, and deafness.

[citation needed] XDR-TB is associated with a much higher mortality rate than MDR-TB, because of a reduced number of effective treatment options.

[17][18] One regimen for XDR-TB called Nix-TB, a combination pretomanid, bedaquiline, and linezolid,[19] has shown promise in early clinical trials.

[20] Successful outcomes depend on a number of factors including the extent of the drug resistance, the severity of the disease and whether the patient's immune system is compromised.

[10] Carriers who refuse to wear a mask in public have been indefinitely involuntarily committed to regular jails, and cut off from contacting the world.

[citation needed] XDR-TB is defined as TB that has developed resistance to at least rifampicin and isoniazid (resistance to these first line anti-TB drugs defines multidrug-resistant tuberculosis, or MDR-TB), as well as to any member of the quinolone family and at least one of the following second-line anti-TB injectable drugs: kanamycin, capreomycin, or amikacin.

[30] The earlier definition of XDR-TB as MDR-TB that is also resistant to three or more of the six classes of second-line drugs,[15] is no longer used, but may be referred to in older publications.

[32] This was the first epidemic for which the acronym XDR-TB was used, and although TB strains that fulfill the current definition have been identified retrospectively,[33][34] this was the largest group of linked cases ever found.

[35] It is clear that the spread of this strain of TB is closely associated with a high prevalence of HIV and poor infection control; in other countries where XDR-TB strains have arisen, drug resistance has arisen from mismanagement of cases or poor patient compliance with drug treatment instead of being transmitted from person to person.