Table 1.
Fungi associated with pulmonary infections and their characteristic morphology in clinical specimens by direct microscopic examination
| Fungal Group and Representative Pathogens | Microscopic Morphology in Clinical Specimens |
|---|---|
| YEASTS | |
|
| |
| Cryptococcus neoformans | Spherical budding yeasts of variable size, 2–15 μm in diameter. Capsule may be present or absent. No hyphae or pseudohyphae. |
| Trichosporon | Hyaline arthroconidia, blastoconidia, and pseudohyphae, 2–4 by 8 μm. |
|
| |
| MOULDS | |
|
| |
| Mucormycotinaa | Broad, thin-walled, pausi-septate hyphae, 6–25 μm wide with non-parallel sides and random branches. |
| Absidia | |
| Cunninghamella | |
| Mucor | |
| Rhizomucor | |
| Rhizopus | |
| Saksenaea | |
|
| |
| Hyaline Hyphomycetes | |
| Aspergillus | Hyaline, septate, dichotomously branching hyphae of uniform width (3–6 μm). |
| Acremonium | |
| Fusarium | Aspergillus may produce conidial heads in specimens from cavitary pulmonary lesions. Adventitious conidiation may be visualized on histopathologic examination of some of the non-Aspergillus hyphomycetes. |
| Paecilomyces | |
| Phialemonium | |
| Scedosporium | |
| Scopulariopsis | |
| Trichoderma | |
|
| |
| Dematiaceous Hyphomycetes | |
| Alternaria | Pigmented (brown, tan, or black), septate hyphae, 2–6 μm wide. |
| Bipolaris | |
| Curvularia | |
| Cladophialophora | |
| Dactylaria | |
| Exophiala | |
| Phialophora | |
| Ramichloridium | |
| Wangiella | |
|
| |
| OTHER | |
|
| |
| Dimorphic (geographically restricted) Fungi | |
| Blastomyces dermatitidis | Large (8–15 μm diameter) thick-walled budding yeast cells. The junction between mother and daughter cells is typically broad-based. Cells may appear multinucleate. |
| Coccidioides immitis | Spherical, thick-walled spherules, 20–30 μm diameter. Mature spherules contain small, 2–5 μm diameter endospores. Released endospores may be mistaken for yeast. Arthroconidia and hyphae may form in cavitary lesions. |
| Histoplasma capsulatum | Small (2–4 μm diameter), intracellular, budding yeasts. |
| Paracoccidioides brasiliensis | Large (2–30 μm diameter), multiple-budding yeasts ; 12 or more narrow neck buds of variable size may arise from the mother cell. |
| Penicillium marneffei | Oval, intracellular yeast cells bisected with a septum (fission yeast). |
| Sporothrix schenckii | Elongated or “cigar-shaped” yeast cells of varying size (rare). Tissue reaction forms asteroid bodies. |
| Pneumocystis jiroveci | Cysts are round, collapsed, or crescent shaped. Trophozoites seen on staining with giemsa or immunofluorescent stains. |
a
Moulds of the subphylum Mucormycotina, previously referred to as Zygomycetes