Question 1

Question

A 38-year-old man from the Mississippi River Valley presents with a 3-week history of fever, night sweats, and weight loss. He works as a cave explorer. Chest CT shows mediastinal lymphadenopathy and multiple pulmonary nodules. Bronchoalveolar lavage is performed and a silver stain of the specimen reveals small (2–4 µm) oval yeast forms within the cytoplasm of alveolar macrophages. Cultures at 25°C grow a mold with tuberculate macroconidia. Which of the following correctly describes the tissue form of this organism and its mechanism of immune evasion?

Accepted Answer

Small intracellular yeast at 37°C; survives within macrophages by modulating phagolysosomal pH, scavenging reactive oxygen species, and resisting intracellular killing

Answer

Broad-based budding yeast at 37°C; evades immunity by producing a thick polysaccharide capsule that inhibits phagocyte oxidative burst

Answer

Spherule containing endospores at 37°C; resists phagocytosis by releasing endospores that overwhelm macrophage capacity

Answer

Cigar-shaped yeast at 37°C; introduced via traumatic inoculation and spreads along lymphatic channels

Answer

Pseudohyphae at 37°C; evades immunity by secreting a toxin that directly lyses macrophage nuclei before phagocytosis can occur

Normal flora — MCQs

Normal flora — MCQs

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