Extremely Drug Resistant TB

It isn't good.


Tuberculosis had seemed like it was going away. Medications to cure  the disease. Few are sick to transmit the disease because the drugs are so effective.

The medications, though, need to be taken daily. Multiple pills need to be taken for at least 6 months. A lot of things can happen over that time.

Doses are missed. Pills are vomited; some are not absorbed. Regimens are abandoned; patients stop taking meds.

Pills don't work because patients have weak immune systems and couldn't fight off TB strains. Others just have bad luck.

Resistant strains develop - and then they accumulate. After decades of TB treatment, more and more resistant strains have compounded.

First came resistance to the first line medications, then came resistance to the second line medications. Drug resistance made regimens that used to work not work. New medications were added, new resistances developed. This continued and the world discovered it had XDR TB.

What is XDR TB?

XDR TB stands for Extensively Drug-Resistant Tuberculosis. It is resistant to more drugs than Multidrug-Resistant Tuberculosis (MDR TB).

MDR TB is resistant (at least) to the two most important drugs in TB treatment -  Isoniazid (INH) and Rifampin.

XDR TB is resistant (at least) to the drugs MDR is resistant to (Isoniazid and Rifampin) as well as a Fluoroquinolone (which include Levofloxacin, Moxifloxacin, or Ciprofloxacin) and one (or more) of the injectable drugs used in 2nd line treatment (amikacin, kanamycin, and capreomycin).

Can XDR TB be treated?

Yes. Cases of XDR TB can be treated and cured. Many do survive.

However, may do not survive XDR TB.

The outbreak that first brought attention to XDR TB was in 2006 in Tugela Ferry in KwaZulu-Natal, South Africa. It was found that 52 out of 53 infected died - and died quickly. Once samples to test for XDR TB were taken - ie sputum samples, most died about 2 weeks later (median 16 days after sputum collection).

Those who died included 6 healthcare workers.

To this day, XDR likely kills many who are never tested, others who die before receiving results, and still others soon after starting treatment before it had time to work. Some who develop the disease do not have access to the medical care needed to quickly diagnose and treat the disease. Diagnosis is often late. Likely most still die from the disease

There are treatment options. Treatment is based on what drugs are still potentially effective. XDR strains can have different drug resistance patterns. The medications used are usually not first choice medications. Many have serious side effects - such deafness or effects on mental health.

The success of treatment depends on how late the infection is diagnosed (ie some are diagnosed after death), whether the person has a weak immune system (such as from HIV), which drugs are effective against the particular XDR TB strain, and how well the patient is able to tolerate the medications.

Who is vulnerable to XDR TB?

Those who

  • Miss TB medication doses.
  • Do not finish their TB regimens.
  • Do not absorb their medications.
  • Become sick again with TB (even if they took their medications).
  • Are from or visited an area where XDR TB is found.
  • Are exposed to someone who has XDR TB.
  • Are immunocompromised, such as with HIV.
  • Are exposed to multiple people with TB at the same time (with different strains, such as in a TB treatment center)

TB sometimes spreads in crowded indoor spaces, such as homes with many occupants and little sunlight, hospitals, prisons, homeless shelters. XDR TB can spread in the same environments.

Has there been XDR TB in the US?


There's very low risk of catching XDR TB in the US, though. There were 63 cases reported between 1993 and 2011.

How many cases are there worldwide?

Fortunately, XDR TB is rare. It is thought roughly 9 percent of MDR-TB cases are XDR-TB. This means there are over 50,000 cases at any time (9% of among the 650,000 MDR cases at any time). MDR usually makes up about 14% of TB cases, but in areas of the old Soviet Union, it is often more. Among patients previously treated for TB in what once were Soviet Union countries, over 1 in 2 may have MDR TB.

Where else has XDR TB been found? 

By 2012, 84 countries had reported at least 1 case of XDR TB. Cases have particularly been found in India, China, and South Africa. Cases have been found, however, all over the world from Argentina to Uzbekistan to the UK, France, Germany, and Italy, as well as Peru, Pakistan, and the Philippines, among many others.

There have also been cases of what has been called TDR (totally - or extremely - drug resistant TB (XXDR TB)). These cases involve even further resistance, with potentially no  successful treatment regimens available. The WHO however has not yet made the term official and there is not an official definition.

The disease was seen in two young women in Italy, who were not treated initially with the medications they should have been. Other cases were identified in Iran and later India

How does XDR spread?

It is spread by breathing. The TB bacteria can fly into the air when someone coughs, sneezes, talk, or even just breathes. TB is an airborne infection. This means the bacteria that cause TB can float in the air for hours and hours. Those who breathe in the air where TB is floating can become infected. About 1 in 3 people around the world do become infected. Each case of infectious pulmonary TB is expected to lead to maybe 10 other cases.

What isn't a risk?

Those who have been treated effectively for TB are not infectious to others. Those who are undergoing treatment should also stop being contagious during treatment if successful (and their doctor or nurse should tell them when they are not infectious). Their plates, glasses, and clothing are not infectious. Healthcare professionals use special N95 masks to avoid breathing in the bacteria when caring for someone who is infectious with XDR TB, but they can shake hands or otherwise touch this person and their personal effects without risk.

Is there a vaccine for XDR TB?

The BCG vaccine, per the CDC, is "not generally recommended in the United States because it has limited effectiveness for preventing the most common forms of TB and in preventing TB in adults."

What if you are exposed to XDR TB?

Talk to your doctor or nurse. There are tests you can do to find out if you have TB bacteria inside of you. Medications may be given to avoid developing TB, if appropriate.

How do hospitals stop the spread of XDR TB?

Hospitals must maintain strict Infection Prevention and Control Practices. Healthcare workers wear N95 masks to prevent breathing in TB when around potentially infectious TB patients. They keep patients isolated from others, potentially with negative pressure rooms to keep the bacteria from floating away and also with other sorts of filters or UV lights (or sunlight and open windows) to reduce the amount of TB bacteria in the air. They also work to quickly diagnose cases of XDR TB, which can take many weeks, depending on the lab capabilities. They also carefully select medications in order to avoid treating TB with too few active drugs which can lead to further drug resistance developing.

Such better monitoring and testing will mean that more cases will be identified, even if there are not more cases actually out there.

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