Which is not a mycobacteria tuberculosis complex organism?
**Core Concept**: Mycobacteria tuberculosis complex (MTBC) is a group of closely related, slow-growing, air-requiring, and acid-fast bacteria that includes the causative agent of Tuberculosis (TB). TB primarily affects the lungs (pulmonary TB) but can affect other organs as well.
**Why the Correct Answer is Right**: The correct answer is **D**. The Mycobacteria tuberculosis complex consists of six main species:
1. **Mycobacterium tuberculosis**: The primary cause of pulmonary and extra-pulmonary TB in humans.
2. **Mycobacterium bovis**: Causes TB in cattle and other mammals, but can infect humans as well, leading to TB meningitis.
3. **Mycobacterium africanum**: Causes TB in humans, with a higher prevalence in West Africa.
4. **Mycobacterium microti**: A rare cause of human TB, found mostly in rodents.
5. **Mycobacterium pinnipedii**: Found in seals and sea lions, can cause TB in humans as well.
6. **Mycobacterium canetti**: As Mycobacterium tuberculosis, it is primarily responsible for causing TB in humans.
**Why Each Wrong Option is Incorrect**:
A. Mycobacterium bovis BCG (Bacille Calmette-Guérin) is a vaccine strain developed from Mycobacterium bovis and is not pathogenic to humans, though it can cause TB in immunodeficient individuals.
B. Mycobacterium kansasii is a rare cause of TB, primarily affecting the lungs and causing a milder infection than Mycobacterium tuberculosis.
C. Mycobacterium avium complex (MAC) comprises several closely related species, including Mycobacterium avium, Mycobacterium intracellulare, and Mycobacterium scrofulaceum. Although they may cause TB in immunocompromised individuals, they are not part of the MTBC.
D. **Mycobacterium intracellulare**: A rare cause of TB, primarily affecting the lungs and causing a milder infection than Mycobacterium tuberculosis. It is not part of the MTBC.
**Clinical Pearl**: Mycobacterium tuberculosis is the only mycobacterium that can cause TB in immunocompetent individuals and is responsible for the vast majority of TB cases globally. The other options are rare causes of TB in immunocompromised individuals or rarely cause mild infections in immunocompetent individuals.