Which of the following is an acid fast bacteria that is associated with night sweats, fever, and weight loss?

• A. Actinomyces
• B. Mycobacteria
• C. Neisseria gonorrhoeae
• D. Chlamydia trachomatis

Answer: (B)

Acid-fast bacteria have a waxy, mycolic-acid–rich cell wall that resists decolorization with acid-alcohol, so they retain the primary stain when using methods like Ziehl-Neelsen or auramine-rhodamine staining. This staining property is a hallmark used to identify Mycobacterium, the genus that includes the tuberculosis pathogen. The clinical clue of night sweats, fever, and weight loss is classic for tuberculosis, an infection caused by this acid-fast bacillus, which explains why this organism is the best match. The other organisms listed do not have acid-fast cell walls and are associated with different diseases or presentations: Actinomyces is non–acid-fast and forms sulfur granules; Neisseria gonorrhoeae is a Gram-negative diplococcus; Chlamydia trachomatis is an intracellular bacterium without acid-fast staining.