3.11 Nocardia and Actinomyces (Branching Filamentous Species)

Microbiology review for the USMLE Step 1 exam

• Nocardia and Actinomyces are two gram positive bacteria that grow in filaments, resembling fungal hyphae.
• Both are associated with chronic pulmonary lesions, subcutaneous abscesses, and multiple draining sinuses.
• Both are capable of producing sulfur granules.
• Actinomyces is anaerobic and colonizes the mouth, GI, and urinary tracts. It can cause "lumpy jaw syndrome" and requires a long course of high dose penicillin.
• Nocardia is aerobic and stains weakly acid fast. It is found in the environment and typically causes cutaneous disease in immunocompetent individuals and pulmonary disease in immunocompromised individuals.
• Treatment for Nocardia typically involves a combination of antibiotics such as sulfonamides and trimethoprim-sulfamethoxazole.
• SNAP mnemonic: Sulfa for Nocardia; Actinomyces gets Penicillin.