Characteristic Features of Fungi Seen in Direct Examination of Clinical Specimens: Flashcards
Small; oval to round budding cells; often found clustered in histiocytes; difficult to detect when present in small numbers
Histoplasma capsulatum
Small; oval to round to cigar-shaped; single or multiple buds present; uncommonly seen in clinical specimens.
Sporothrix spp.
Cells exhibit great variation in size; usually spherical but may be football-shaped; buds single or multiple and “pinched off”; capsule may or may not be evident; occasionally, pseudohyphal forms with or without a capsule may be seen in exudates of cerebrospinal fluid.
Cryptococcus spp.
Small; bottle-shaped cells, buds separated from parent cell by a septum; emerge from a small collar.
Malassezia furfur (in fungemia)
Cells are usually large, double refractile when present; buds usually single; however, several may remain attached to parent cells; buds connected by a broad base.
Blastomyces spp.
Cells are usually large and are surrounded by smaller buds around the periphery (“mariner’s wheel appearance”); smaller cells may be present (2-5 μm) and resemble H. capsulatum; buds have “pinched-off” appearance
Paracoccidioides brasiliensis
Spherules vary in size; some may contain endospores, others may be empty; adjacent spherules may resemble Blastomyces spp.; endospores may resemble H. capsulatum but show no evidence of budding; spherules may produce multiple germ tubes if a direct preparation is kept in a moist chamber greater than/equal to 24 hr.
Coccidioides spp.
Large, thick-walled sporangia containing sporangiospores are present; mature sporangia are larger than spherules of Coccidioides; hyphae may be found in cavitary lesions.
Rhinosporidium seeberi
(protozoan pathogen that is studied in mycology)
Cells usually exhibit single budding; pseudohyphae, when present, are constricted at the ends and remain attached like links of sausage; hyphae, when present, are septate.
Candida spp. except Candida glabrata
Short, curved hyphal elements are usually present, along with round yeast cells that retain their spherical shape in compacted clusters; “spaghetti and meatballs.”
M. furfur (in tinea versicolor)
Hyphae are large, ribbonlike, often fractured or twisted; occasional septa may be present;
smaller hyphae are confused with those of Aspergillus spp., particularly Aspergillus flavus
Mucorales: Mucor, Rhizopus, and other genera
Hyaline, septate hyphae are commonly seen;
chains of arthroconidia may be present.
Dermatophytes, skin and nails
Arthroconidia on periphery of hair shaft producing a sheath indicate ectothrix infection; arthroconidia formed by fragmentation of hyphae in the hair shaft indicate endothrix infection.
Long hyphal filaments or channels in the hair shaft indicate favus hair infection.
Dermatophytes, hair
Hyphae are septate and exhibit dichotomous, 45-degree branching; larger hyphae, often disturbed, may resemble those of Mucorales.
Aspergillus spp.
Hyphae and rectangular arthroconidia are present and sometimes rounded; irregular forms may be present
Geotrichum spp.
