Histoplasma and Dimorphic Fungi

A 38-year-old male farmer from Madhya Pradesh presents with a 3-week history of progressive dyspnea, fever (38.5°C), and a nonproductive cough. He reports exposure to bird droppings while cleaning poultry sheds. Chest X-ray shows bilateral hilar lymphadenopathy with diffuse micronodular infiltrates. Sputum smear microscopy is negative for acid-fast bacilli. A bronchoalveolar lavage (BAL) specimen is sent for fungal culture and histopathology. On KOH mount of BAL fluid, small (2–4 μm), oval, intracellular yeast cells with a characteristic "halo" or clear zone around them are seen within macrophages. Culture on Sabouraud dextrose agar at 37°C grows small, white, mold-like colonies. What is the most likely causative organism?

A 42-year-old immunocompromised male (CD4 count 85 cells/μL) from a cave-dwelling region in Himachal Pradesh presents with a 4-week history of fever, weight loss, hepatosplenomegaly, and pancytopenia. Blood cultures and bone marrow aspirate smears show numerous small (2–4 μm), oval yeast cells within macrophages and monocytes. Fungal culture on Sabouraud dextrose agar at 37°C is pending. The patient is started on empirical antifungal therapy. Which of the following is the drug of choice for disseminated histoplasmosis in this severely immunocompromised patient?

Histoplasma capsulatum is classified as a dimorphic fungus. At what temperature does it exist as a yeast form in human tissue?

Which of the following is the characteristic microscopic feature of Histoplasma capsulatum yeast cells when observed within infected macrophages?