Which of the following is not a rapidly growing atypical mycobacteria causing lung infections –
**Core Concept**
Atypical mycobacteria (also known as non-tuberculous mycobacteria, NTBMs) are a group of bacteria that can cause lung infections, particularly in immunocompromised individuals. Rapidly growing atypical mycobacteria are characterized by their ability to grow in culture within 7 days, in contrast to slowly growing species that require longer incubation periods.
**Why the Correct Answer is Right**
M. kansasii is a slowly growing atypical mycobacterium that can cause lung infections, but it typically requires 3-6 weeks to grow in culture. In contrast, the other options (M. chelonae, M. fortuitum, and M. abscessus) are rapidly growing atypical mycobacteria that can cause lung infections and grow in culture within 7 days. M. kansasii is more commonly associated with pulmonary disease in immunocompetent individuals and is often considered a "slow-growing" mycobacterium due to its growth rate.
**Why Each Wrong Option is Incorrect**
**Option A:** M. chelonae is a rapidly growing atypical mycobacterium that can cause skin and soft tissue infections, as well as lung infections in immunocompromised individuals. It is known for its ability to grow rapidly in culture, typically within 3-7 days.
**Option B:** M. fortuitum is another rapidly growing atypical mycobacterium that can cause skin and soft tissue infections, as well as lung infections in immunocompromised individuals. It is known for its ability to grow rapidly in culture, typically within 3-7 days.
**Option C:** M. abscessus is a rapidly growing atypical mycobacterium that can cause lung infections, particularly in immunocompromised individuals. It is known for its ability to grow rapidly in culture, typically within 3-7 days.
**Clinical Pearl / High-Yield Fact**
It's essential to note that rapidly growing atypical mycobacteria (such as M. chelonae, M. fortuitum, and M. abscessus) are more commonly associated with skin and soft tissue infections, whereas slowly growing species (such as M. kansasii) are more commonly associated with pulmonary disease.
**✓ Correct Answer: D. M.kansasii**