M. avium intracellulare is: September 2009
**Question:** M. avium intracellulare is: September 2009
**Core Concept:** Mycobacterium avium intracellulare is a type of mycobacterium, a genus of bacteria that includes both pathogenic and non-pathogenic species. It is a slow-growing, acid-fast bacteria that can cause infections in humans.
**Why the Correct Answer is Right:** M. avium intracellulare refers to a specific strain of M. avium that primarily affects the lungs and can cause a form of pulmonary infection called M. avium complex (MAC) disease. The term "intracellulare" refers to its ability to invade and survive within host cells. The year "September 2009" is not relevant to the correct answer but might be a reference to the year when the World Health Organization (WHO) classified MAC as a group of organisms with potential pandemic potential due to its ability to cause severe respiratory infections in immunocompromised individuals.
**Why Each Wrong Option is Incorrect:**
A. M. abscessus: This is another slow-growing mycobacterium, but it is distinct from M. avium intracellulare and has different clinical characteristics and antibiotic resistance patterns.
B. M. tuberculosis: This is another slow-growing mycobacterium but is responsible for causing tuberculosis (TB) disease, which is caused by a different set of mycobacteria (Mycobacterium tuberculosis) and presents with a distinct clinical picture.
C. MAC (M. avium complex): As mentioned earlier, MAC includes both M. avium and M. intracellulare. M. avium intracellulare is a specific strain within the MAC group.
D. M. kansasii: This is a different slow-growing mycobacterium that causes pulmonary infections but is distinct from M. avium intracellulare and has different clinical characteristics and antibiotic resistance patterns.
**Clinical Pearl:** Immunocompromised individuals, particularly those with acquired immunodeficiency syndrome (AIDS), are at a higher risk of developing severe pulmonary infections caused by MAC, including M. avium intracellulare. Early diagnosis and appropriate antibiotic treatment are crucial for managing these infections effectively.