Nocardia can be differentiated from Actinomyces based on

• A. Nocardia being an obligate anaerobe
• B. The partial-acid fast staining reaction of Actinomyces
• C. The production of sulfur granules in cases of nocardiosis
• D. Nocardia being catalase positive

Answer: (D)

Distinguishing Nocardia from Actinomyces relies on an enzymatic difference that labs can rapidly test. Nocardia is catalase positive, meaning it readily breaks down hydrogen peroxide, while Actinomyces is catalase negative. This difference provides a reliable, quick way to tell them apart when you’re looking at Gram-positive branching bacteria.

Additional context that helps understanding: Nocardia is aerobic and partially acid-fast, whereas Actinomyces is anaerobic and not acid-fast, and sulfur granules are more characteristic of Actinomyces infections. But the catalase test gives a clear, practical distinction between the two.