Epidemic marker of TB –
**Core Concept**
The question is referring to a specific indicator used to determine the spread of tuberculosis (TB) in a population. TB is a bacterial infection caused by Mycobacterium tuberculosis, which primarily affects the lungs but can also affect other parts of the body. The epidemic marker of TB is a key concept in epidemiology and public health.
**Why the Correct Answer is Right**
The correct answer is **Isoniazid Resistance**. Isoniazid is a first-line antitubercular medication used to treat TB. The development of isoniazid resistance in M. tuberculosis is a significant concern as it indicates that the bacteria have mutated and can survive despite treatment. This resistance is often seen in areas with high TB prevalence and can be a marker of an ongoing TB epidemic. Isoniazid resistance is typically measured through drug susceptibility testing, which involves exposing M. tuberculosis to isoniazid and observing its growth.
**Why Each Wrong Option is Incorrect**
**Option A:** **TB Skin Test Positivity**. While the TB skin test (Mantoux test) can indicate exposure to TB, it is not a specific marker of an epidemic.
**Option B:** **TB Mortality Rate**. TB mortality rate is an important indicator of TB control, but it is not a specific marker of an epidemic.
**Option C:** **TB Prevalence**. TB prevalence is an essential measure of the burden of TB in a population, but it is not a specific marker of an epidemic.
**Clinical Pearl / High-Yield Fact**
Remember that isoniazid resistance is a key indicator of TB transmission and can be used to monitor the effectiveness of TB control programs.
**Correct Answer:** . Isoniazid Resistance