The key difference between MDR and XDR-TB is that MDR-TB is due to tuberculosis bacteria that are resistant to first-line anti-TB drugs, while XDR-TB is due to tuberculosis bacteria that are resistant to both first-line and second-line anti-TB drugs.
Tuberculosis (TB) is a serious infectious lung disease. It is a potentially life-threatening condition caused by a bacterium called Mycobacterium tuberculosis. It is spread from person to person through tiny droplets released into the air via coughs and sneezes. TB is usually treated with combinations of antibacterial medications for six to twelve months. However, TB also remains a major killer disease due to the increase of drug-resistant bacterial strains. MDR and XDR-TB are two types of drug-resistant tuberculosis due to drug-resistant bacterial strains.
CONTENTS
1. Overview and Key Difference
2. What is MDR-TB
3. What is XDR-TB
4. Similarities – MDR and XDR-TB
5. MDR vs XDR-TB in Tabular Form
6. Summary – MDR vs XDR-TB
What is MDR-TB?
MDR-TB (multidrug-resistant tuberculosis) is due to tuberculosis bacteria that are resistant to first-line anti-TB drugs. Normally, TB is treated with four standard first-line anti-TB drugs: isoniazid, rifampin, pyrazinamide, and ethambutol. MDR-TB is a form of tuberculosis (TB) infection that is caused by bacteria that are resistant to treatment with at least two of the most potent first-line anti-TB drugs, such as isoniazid and rifampin. Some strains of TB bacteria have developed resistance to standard drugs through genetic changes. Therefore, some mechanisms of drug resistance include cell walls that have complex lipid molecules that act as a barrier for drugs, drug modifying and inactivating enzymes, drug efflux systems, and spontaneous mutations.
Figure 01: MDR-TB
Currently, the majority of multidrug-resistant TB cases are due to one strain of TB bacteria belonging to the Beijing lineage. MDR-TB accelerates if incorrect treatments are used, which leads to the development and spread of multidrug-resistant TB. Treatment of MDR-TB involves the use of second-line antibacterial drugs that are less effective, more toxic, and much more expensive than first-line drugs.
What is XDR-TB?
XDR-TB (extensively drug-resistant tuberculosis) is due to tuberculosis bacteria that are resistant to both first-line and second-line anti-TB drugs. XDR-TB strains have arisen due to mismanagement of individuals with multidrug-resistant TB (MDR-TB). XDR-TB can develop when second-line drugs that are used to treat MDR-TB are also misused or mismanaged and become ineffective. Some strains of TB bacteria that cause XDR-TB belong to Euro-American, Central Asian, and Beijing lineages.
Figure 02: XDR-TB
Some mechanisms that are used by extensively drug-resistant tuberculosis bacteria include cell walls that have complex lipid molecules that act as a barrier for drugs, drug modifying and inactivating enzymes, slow metabolism mechanism, and drug efflux systems. One treatment regimen for treating XDR-TB includes using a combination of pretomanid, bedaquiline, and linezolid. In addition, the BCG vaccine is also effective against XDR-TB.
What are the Similarities Between MDR and XDR-TB?
- MDR and XDR-TB are two types of drug-resistant tuberculosis due to drug-resistant bacterial strains.
- TB bacterial strains causing both MDR and XDR-TB are resistant to first-line drugs such as isoniazid, rifampin.
- Both drug-resistant tuberculosis types occur due to misused and mismanagement of TB drugs that become ineffective.
- Both drug-resistant tuberculosis types cause accelerated death rates due to TB worldwide which lead to a huge global burden.
What is the Difference Between MDR and XDR-TB?
MDR-TB is due to tuberculosis bacteria that are resistant to first-line anti-TB drugs, while XDR-TB is due to tuberculosis bacteria that are resistant to both first-line and second-line anti-TB drugs. Thus, this is the key difference between MDR and XDR-TB. Furthermore, MDR-TB cases are mainly due to one strain of TB bacteria that belongs to the Beijing lineage. On the other hand, XDR-TB cases are mainly due to some strains of TB bacteria that belong to Euro-American, Central-Asian, and Beijing lineages.
The below infographic presents the differences between MDR and XDR-TB in tabular form for side by side comparison.
Summary – MDR vs XDR-TB
MDR and XDR-TB are two types of drug-resistant tuberculosis due to drug-resistant bacterial strains. MDR-TB is due to tuberculosis bacteria that are resistant to first-line anti-TB drugs, while XDR-TB is due to tuberculosis bacteria that are resistant to both first-line and second-line anti-TB drugs. So, this is the key difference between MDR and XDR-TB.
Reference:
1. “Extensively Drug Resistant Tuberculosis.” An Overview | ScienceDirect Topics.
2. “Multidrug Resistant Tuberculosis.” An Overview | ScienceDirect Topics.
Image Courtesy:
1. “Multidrug-Resistant Tuberculosis (MDR TB) and Possible Effective Treatments (5102307287)” By NIAID – (CC BY 2.0) via Commons Wikimedia
2. “Extensively Drug-Resistant Tuberculosis (XDR TB) Diminishing Options for Treatment (5102295715)” By NIAID (CC BY 2.0) via Commons Wikimedia