In TB classification based on drug susceptibility, what does multi-drug resistant mean?

Multi-drug resistant tuberculosis (MDR-TB) specifically refers to the strain of Mycobacterium tuberculosis that is resistant to at least two of the most potent first-line anti-TB agents: isoniazid and rifampicin. These two drugs are critical components of standard TB treatment regimens, and their resistance significantly complicates therapy and increases the risk of transmission as well as poor treatment outcomes.

Understanding this definition is crucial for effective tuberculosis control measures, as MDR-TB requires more complex and often prolonged treatment regimens, which may include second-line drugs that are less effective, more toxic, and more expensive. Therefore, accurately identifying MDR-TB cases is essential for appropriate management and for implementing strategies to limit the spread of these resistant strains in the population.