Question

A patient presented with complaints of persistent cough and weight loss. He had a history of contact with multiple sexual partners. He was diagnosed as HIV positive 6 months back and is poorly adherent to his medications. The fungal culture of sputum was negative. On Gomori methamine silver staining, the cells showed darkly stained crescent-shaped cysts. What is the most likely causative organism?

• A. Paracoccidiodes brasiliensis
• B. Histoplasma capsulatum
• C. Coccidiodes immitis
• D. Pneumocystis jerovecii

Answer 1

The Correct Option is D

In this clinical scenario, the patient presents with persistent cough and weight loss, along with a history of being diagnosed as HIV positive 6 months prior. The patient is noted to be poorly adherent to his medications. These factors suggest immunosuppression, which increases susceptibility to opportunistic infections.

The fungal culture of sputum being negative indicates that the organism might not be a typical culture-positive fungus. This data aligns with the presented staining results: the Gomori methenamine silver staining shows darkly stained crescent-shaped cysts, which are characteristic of Pneumocystis jirovecii. This organism is often linked with Pneumocystis pneumonia (PCP), a common opportunistic infection in HIV-positive individuals.

Analysis of Options:

• Paracoccidiodes brasiliensis: Typically endemic to South America, associated with paracoccidioidomycosis. Noted for yeast cells with multiple buds resembling a "pilot wheel," visible in a specific tissue stain, not Gomori methenamine silver.
• Histoplasma capsulatum: Found in soil contaminated with bird or bat droppings, leads to histoplasmosis. Visibility as small intracellular yeasts in tissue.
• Coccidiodes immitis: Causes coccidioidomycosis, often diagnosed via spherules in tissue secretions.
• Pneumocystis jirovecii: Identified by Gomori methenamine silver stain showing cysts, common in HIV patients with low CD4 counts.

The staining pattern and patient profile strongly indicate Pneumocystis jirovecii as the causative organism, making it the most likely possibility in this case.