Question

CASE C: A 61 year old African American male presents to the emergency department with complaints of a productive cough, dyspnea and altered mental status. His past medical history is significant for HIV and currently he is non-compliant with his anti-retroviral medications. On arrival, he is found to be hypoglycemic (glucose 49 mg/dL) and tachycardic (heart rate between 160-180 beats/min). He lives in a group home and they report decreased oral intake for several days but he denies fever, chills, chest pain or abdominal pain. He is a tobacco smoker and admits to previous illicit drug use. On physical exam, he is lethargic and respiratory auscultation reveals coarse lung sounds, bilaterally. A chest x-ray shows bilateral interstitial and airspace opacities suggestive of an infectious process. His CD4 count is markedly decreased at 3 cells/cmm. Peripheral blood and bronchoalveolar lavage (BAL) fluid are sent to the hematology and cytology laboratories for microscopic examination. Blood and BAL specimens were also transported to the microbiology lab for bacterial, fungal and mycobacterial cultures Both the peripheral blood smear and BAL showed intracellular, small, ovoid yeast cells with narrow based budding. The mold form grew on Sabouraud dextrose, SAB with chloramphenicol and Mycosel agars. Microscopic morphology of a lactophenol cotton blue prep illustrated septate hyphae bearing round to pear-shaped microconidia as well as tuherculate thick-walled macroconidia Q1. Explain/Discuss and give the reasons, as presented in the case history, the most likely fungal agent associated with this patient. Q2. Illustrate, label and describe the microscopic finds of the culture of the suspect organism at 37 C and 25 C Q3. Is this organism considered to be dimorphic? Explain, in details, the reasons for your response Q4. Identify the antifungal agents which may possibly be used to treat the fungal infection Case 7

Answer 1

Ans 1: On the basis of patient history, The most likely fungus is Histoplasma capsulatum because of the HIV patient is more prone to infect with this fungus. The microscopical characteristics suggest the features of the same fungus.

Ans 2: when the microbes are cultured in the laboratory at 25°C, H. capsulatum is a filamentous mold and shows both pear shaped microconidia (2-5 µm) and thick walled macroconidia that exhibits the characteristic tubercles or projections on the surface (8-15 µm). The yeast phase occurs in the tissue. The temperatures above 35°C the yeast phase is characterized as small oval budding cells with 2-4 µm in diameter and are usually occurs in clusters within the macrophages.

Ans 3: Yes, It is a dimorphic fungus because it exists in both yeast and mold forms. when the microbes are cultured in the laboratory at 25°C, H. capsulatum is a filamentous mold. When the same microbe is cultured at the temperatures above 35°C, H. capsulatum is the yeast and is characterized as small oval budding cells.

Ans 4: If the infection is disseminated then Amphotericin B is the best choice. In case of less severe infection, the itraconazole is commonly used.