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Actinomycosis Penicillin — SCE Infectious Diseases MCQ

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EasyRespiratory InfectionActinomycosis PenicillinSCE Infectious Diseases

A 50-year-old man presents with a slowly progressive right-sided facial mass that has been present for 18 months. It drains thick, purulent material through a sinus tract. He has poor dentition and a recent dental extraction. CT shows a destructive right mandibular lesion extending into the soft tissues. Tissue biopsy shows sulphur granules. Culture grows a branching Gram-positive filamentous organism on anaerobic culture after 14 days. What antibiotic has the best activity?

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Correct answer: B — IV Benzylpenicillin (or IV Amoxicillin) — Actinomyces is exquisitely penicillin-sensitive; prolonged therapy (6–12 months total) is needed

Actinomyces israelii is exquisitely penicillin-sensitive — Benzylpenicillin (or Amoxicillin) is the drug of choice. The key to successful treatment is DURATION, not drug potency: IV Benzylpenicillin for 2–6 weeks then oral Amoxicillin for a total of 6–12 months. Short courses result in relapse. Actinomycosis is often mistaken for malignancy due to its mass-like presentation with tissue destruction. Surgical debridement may be needed for extensive disease. Doxycycline, Erythromycin, and Clindamycin are alternatives for penicillin allergy.

Reference: BSAC 2017 – Actinomycosis; BNF 2024 – Actinomyces treatment