]> 2026-07-31T11:51:59+00:00 WBR0186 0 en ''Histoplasma capsulatum'' ''Histoplasma capsulatum'' is a dimorphic fungus that forms hyphae with microconidia and tuberculate macroconidia. It does not form spherules with endospores. Histoplamsa microconidia are much smaller than the spherules of Coccidioides species. They can be observed inside macrophages as they grow and multiply in the phagosome. ''Blastomyces dermatitidis'' ''Blastomyces dermatitidis'' form hyphae with nondescript conidia. The tissue form is a broad-based budding yeast. ''Coccidioides immitis'' ''Coccidioides immitis'' is a dimorphic fungus that forms characteristic spherules with endospores inside host tissues. ''Aspergillus fumigatus'' ''Aspergillus fumigatus'' is a monomorphic filamentous fungus that forms dichotomously branching septate hyphae at 45 degree angle. Cryptococcus neoformans ''Cryptococcus neoformans'' is an encapsulated monomorphic yeast. It does not form spherules with endospores. Microbiology A 40-year-old woman presents to the physician’s office for several weeks of cough and intermittent fever. Initial work-up reveals a heterogeneous right lower lobe mass, hilar lymphadenopathy, and a left-sided pleural effusion on chest x-ray. Bronchoscopy with transbronchial biopsy reveals necrotic lung tissue with spherules containing hundreds of uninucleated endospores. Which of the following is the most likely causative organism? C Infectious Disease 2020-10-27T23:38:35Z 2459150.4851273 WBR0186