Sulfur granules are characteristic of pus from infections with which organism?

• A. Nocardia
• B. Actinomyces
• C. Streptococcus
• D. Staphylococcus

Answer: (B)

Sulfur granules in pus point to an Actinomyces infection, classically Actinomyces israelii. These granules are yellowish clumps of the organism embedded in necrotic debris that form in chronic, suppurative infections and draining sinus tracts, especially in cervicofacial actinomycosis. Actinomyces are anaerobic, gram-positive, filamentous bacteria that normally reside in the oral cavity; when they invade tissue after dental work or trauma, they produce characteristically long, branching filaments and the distinctive sulfur granules in the purulent discharge.

Other common pus-forming bacteria don’t typically produce sulfur granules; for example, Staphylococcus and Streptococcus cause suppurative infections without these granules. Nocardia can form branching filaments and is weakly acid-fast, but sulfur granules are the hallmark seen with Actinomyces infections.