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

Actinomycosis sounds fungal because of its name, but Actinomyces israelii is actually a branching, filament forming bacterium. Treatment choice depends on which drug reliably kills this organism and can reach deep, scarred chest tissue.

1. Amphotericin B: This is a strong antifungal drug used for infections like aspergillosis or candidiasis. Since actinomycosis is bacterial, this drug has no target here.
2. Penicillin: Actinomyces species remain highly sensitive to penicillin, and high dose intravenous penicillin continued for weeks to months is what actually clears the deep sinus tracts and fibrotic lung or chest wall disease seen in thoracic actinomycosis.
3. Co trimoxazole: This is kept as a backup choice for patients who cannot tolerate penicillin, not as the primary drug.
4. Itraconazole: Like amphotericin B, this is an antifungal agent and does not act on this bacterial infection.

Because Actinomyces is a bacterium and stays sensitive to it, penicillin remains the drug of choice, usually given in high doses for a long duration to penetrate the dense, fibrous thoracic lesions.

Let's summarize:

• Actinomycosis is bacterial, so antifungal drugs like amphotericin B and itraconazole do not work.
• High dose, prolonged penicillin is the standard first line treatment.

The correct answer is penicillin.