All of the following are features of mycobacterium tuberculosis, except :
**Core Concept**
Mycobacterium tuberculosis is a gram-positive, acid-fast bacterium that causes tuberculosis (TB), a chronic infectious disease primarily affecting the lungs but can also affect other parts of the body. The pathogenesis of M. tuberculosis involves the bacteria's ability to survive and replicate within host macrophages, leading to a strong immune response.
**Why the Correct Answer is Right**
The correct answer is related to the fact that M. tuberculosis is an obligate intracellular pathogen, meaning it requires a host cell to survive and replicate. This characteristic is a key feature of M. tuberculosis, allowing it to evade the host's immune system and establish a chronic infection. The bacteria's ability to survive within macrophages is due to its unique cell wall composition, which includes mycolic acids and arabinogalactan, making it resistant to acid decolorization.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because M. tuberculosis is not a gram-negative bacterium. Its gram-positive nature is a key characteristic that distinguishes it from other pathogenic bacteria.
**Option B:** This option is incorrect because M. tuberculosis does not have a flagellum. Its lack of motility is a result of its unique cell wall composition and the absence of flagella.
**Option C:** This option is incorrect because M. tuberculosis is not a spore-forming bacterium. While it does have a complex cell wall, it does not produce spores as a survival mechanism.
**Clinical Pearl / High-Yield Fact**
M. tuberculosis is a classic example of an intracellular pathogen that exploits the host's immune system to establish a chronic infection. Understanding the pathogenesis of M. tuberculosis is crucial for the development of effective treatments and prevention strategies.
**Correct Answer:** D.