Question

The drug of choice for thoracic actinomycosis is

• A. Amphotericin B
• B. Penicillin
• C. Co trimoxazole
• D. Itraconazole

Hint:

Actinomyces israelii is a bacterium, not a fungus, and it is highly sensitive to penicillin given in high dose for a long course.

Answer 1

The Correct Option is B

Step 1: Understanding the Question.
Actinomycosis is a chronic infection that can involve the chest (thoracic actinomycosis), and we are asked for its drug of choice.

Step 2: Key Concept.
Actinomycosis is caused by Actinomyces israelii, a filamentous, branching, gram positive bacterium that behaves like an anaerobe or microaerophilic organism, not a fungus, even though the name sounds fungal. It classically forms sulfur granules in tissue and spreads slowly across natural planes, causing sinus tracts.
Because Actinomyces species are reliably sensitive to penicillin, and the infection tends to be deep seated and fibrotic (poor drug penetration), high dose penicillin given for a long course, often several months, is the standard first line treatment.

Step 3: Detailed Explanation.
Amphotericin B is an antifungal drug. Since actinomycosis is bacterial, not fungal, amphotericin B has no role here.
Co trimoxazole and other agents such as tetracyclines or clindamycin are used mainly as alternatives in patients who are allergic to penicillin, not as the first choice.
Itraconazole is also an antifungal agent and is not active against Actinomyces.
Only penicillin covers Actinomyces reliably and is used at high dose for a prolonged period to clear deep thoracic disease.

Step 4: Final Answer.
The drug of choice for thoracic actinomycosis is penicillin, option (2).