Examine the specimen and smear for sulfur granules. Granules (grains) may range from 0.2-5 mm in size and may be present in primary cutaneous lesions.17
The presence of hard sulfur granules in pus and on direct smears may be seen among infections caused by the anaerobe
Actinomyces. Among the aerobic actinomycetes,
Nocardia and
Streptomyces are known to produce soft sulfur-like granules. Skin biopsies may reveal sulfur granules in an abscess. The granules themselves do not contain sulfur; rather, they are named as such because of their yellow (or white to yellow) grainy appearance. They occur as a result of the body's immune response when granulomatous tissue forms. (Granules of brown, black, or red color may be associated with some fungal organisms.)
Of note, granulomas are the body's immune defense mechanism. This mechanism triggers white blood cells (phagocytes) to "wall off" foreign invaders such as bacteria to prevent spread.
18. CDC. Image #4333. This photomicrograph of an unidentified tissue specimen was harvested from a patient, who had presented with a case of actinomycosis, caused by the Gram-positive, aerobic actinomycete, Streptomyces somaliensis. Note the number of characteristic sulfur granules visible in this view. PHIL public domain. Created 1971. Accessed October 27, 2022. https://phil.cdc.gov/Details.aspx?pid=4333
