Mycobacterium tuberculosis causes tuberculosis (TB), which is an airborne infection that most frequently affects the lungs. TB is contagious and can be passed from one person to another through cough, sneeze, or spittle of those who are infected.
Drug resistance develops when TB medications are used improperly, as a result of incorrect prescription by healthcare professionals, using poor quality medications, or when patients discontinue their treatment too soon.
Types of drug resistant tuberculosis
Mono-resistance: This type of tuberculosis is brought about by bacteria that are resistant one first-line anti-TB drug only.
Poly-resistance: This type of tuberculosis is brought about by bacteria that are resistant to more than one first-line anti-TB drug, other than both isoniazid and rifampicin.
Multidrug resistance (MDR): This type of tuberculosis is brought about by bacteria that are resistant to both rifampicin and isoniazid.
Extensive drug resistance (XDR): This type of tuberculosis is caused by bacteria resistant to any fluoroquinolone, and at least one of the three second-line injectables such as kanamycin, capreomycin, and amikacin, in addition to having multidrug resistance.
Rifampicin resistance (RR): This type of tuberculosis is caused by bacteria resistant to rifampicin, in the form of mono-resistance, poly-resistance, MDR or XDR.
Patients are left with much less effective treatment options because XDR TB is resistant to the strongest TB drugs.
People with HIV infection or other illnesses that can impair their immune system should be cautious of XDR TB. Once infected, these people are more likely to develop TB disease with serious complications that could even result in death.
Symptoms of tuberculosis
The symptoms of TB disease differ based on the stages of infection
- There are no symptoms during the primary TB infection stage, but if the infection persists, it may manifest as flu-like symptoms:
- Low fever
- Cough
- Fatigue
- There are no symptoms and signs of illness during the latent stage
- Symptoms seen during the active TB stage:
- Cough with mucus and blood
- Pain in the chest, while breathing and coughing
- Fever and chills
- Night sweats
- Loss of appetite
- Loss of weight
- Fatigue
People at risk for contracting XDR TB
Drug-resistant tuberculosis (MDR or XDR) is more common in those who:
- Stop taking their TB medications regularly
- Avoid taking all of the TB medications as directed by their healthcare professional
- Had a recurrence of TB disease after taking TB medication in the past
- Come from regions where drug-resistant TB is common
- Have been around a person known to have drug-resistant TB disease
Diagnosis of tuberculosis infection
The TB-PCR is one of the tests that helps in the diagnosis and confirmation of a tuberculosis infection. TB-PCR test uses samples such as blood or sputum to find out if the genetic material of the bacteria is present in the test sample.
TB-PCR test outcomes can be either positive or negative.
Positive TB blood test: It means that TB bacteria’s genetic material was found in the test sample. Further tests may be required to determine whether you have a latent TB infection or a recent TB infection.
Negative TB blood test: It means that TB bacteria’s genetic material was not found in your test sample and you are not having latent TB or a recent TB infection.
Diagnosis of drug-resistant tuberculosis
Drug susceptibility testing (DST) helps evaluate the drug susceptibility or resistance of Mycobacterium tuberculosis bacteria.
Xpert MTB/RIF assay and its successor, the Xpert MTB/RIF Ultra, are widely used throughout the world to identify rifampicin and Mycobacterium tuberculosis resistance, but they are unable to determine resistance to isoniazid and second-line medications.
Xpert MTB/XDR is a rapid nucleic acid amplification test for tuberculosis and drug resistance detection that can be used in lower-level and intermediate laboratories. In samples where Xpert MTB/XDR detects tuberculosis, it can also be used to identify isoniazid, fluoroquinolone, ethionamide, and amikacin resistance.
MTB detected or MTB not detected can be used to describe the results of Xpert MTB/XDR. If the results are indicated as MTB detected, it means resistance was found to certain drug. If the results are indicated as MTB not detected, it means that no drug resistance was found.
Prevention of multi drug-resistant tuberculosis
Take all TB medications exactly as prescribed by your doctor to prevent the spread of drug-resistant TB. There shouldn't be any missed doses or treatment interruptions. Patients getting treatment for TB disease should let their health care provider know if they are having trouble taking the medications.
Healthcare professionals can help prevent drug-resistant TB by promptly diagnosing cases, adhering to advised treatment guidelines, observing patient’s responses to treatment, and ensuring therapy is finished.
Avoiding contact with known drug-resistant TB patients in enclosed or crowded settings, such as hospitals, jails, or homeless shelters, is another way to prevent contracting the disease. Workers in hospitals or other healthcare facilities where tuberculosis patients are likely to be seen should speak with occupational health or infection control specialists.
Multidrug resistant tuberculosis treatment
WHO Consolidated Guidelines on Tuberculosis (TB), Module 4: Treatment - Drug-Resistant Tuberculosis Treatment 2022 update includes two new recommendations for treatment and care for drug-resistant TB (DR-TB) patients.
- 6-month BPaLM regimen made up of bedaquiline, pretomanid, linezolid, and moxifloxacin in patients with multidrug-resistant or rifampicin resistant TB (MDR/RR-TB) and those with additional fluoroquinolone resistance (pre-XDR-TB).
- 9-month all-oral regimen is advised for MDR/RR-TB patients in whom fluoroquinolone resistance has been excluded.
- Currently recommended treatment regimens for isoniazid-resistant TB include longer all oral regimens, the timing of antiretroviral therapy (ART) in MDR/RR-TB patients with HIV infection, monitoring of treatment response and surgery for patients receiving MDR-TB treatment.
According to some TB control programs, between 30% and 50% of individuals who have MDR/ XDR TB can be cured. The degree of drug resistance, the severity of the illness, whether the patient has a compromised immune system, and treatment compliance all play a significant role in the success of the treatment.
