Nocardia can be differentiated from Actinomyces based on which characteristic?

Nocardia can be differentiated from Actinomyces based on which characteristic?

• A. Nocardia obligate anaerobe
• B. Partial-acid fast staining reaction of Actinomyces
• C. Production of sulfur granules in nocardiosis
• D. Nocardia being catalase positive

Answer: (D)

Catalase activity effectively separates these two. Nocardia is catalase-positive, meaning it bubbles when exposed to hydrogen peroxide, which fits its aerobic, more oxidative metabolism. Actinomyces is catalase-negative, aligning with its anaerobic physiology. While other differences exist—Nocardia is partially acid-fast and Actinomyces is not, and sulfur granules are more typical of Actinomyces infections—the catalase test provides the simplest and most reliable single characteristic to distinguish them in the lab.

Catalase activity effectively separates these two. Nocardia is catalase-positive, meaning it bubbles when exposed to hydrogen peroxide, which fits its aerobic, more oxidative metabolism. Actinomyces is catalase-negative, aligning with its anaerobic physiology. While other differences exist—Nocardia is partially acid-fast and Actinomyces is not, and sulfur granules are more typical of Actinomyces infections—the catalase test provides the simplest and most reliable single characteristic to distinguish them in the lab.