In suspected MAC disease, what is the next step in management?

• A. Bronchoscopy with biopsy
• B. Testing for acid-fast bacilli
• C. Start broad-spectrum antibiotics
• D. Observe without treatment

Answer: (B)

When MAC disease is suspected, the priority is to confirm a mycobacterial infection before starting targeted therapy. The next step is to test respiratory specimens for acid-fast bacilli, using smear and culture. Detecting AFB confirms that the illness is due to a mycobacterium and allows species identification and appropriate microbiologic workup. This approach avoids unnecessary broad-spectrum antibiotics and premature treatment, and it guides the longer, specific MAC therapy that typically follows once microbiologic confirmation is achieved. Bronchoscopy with biopsy is more invasive and is usually pursued if initial sputum testing is nondiagnostic or if tissue diagnosis is needed. Observing without treatment isn’t appropriate given ongoing suspicion and potential for progression.