mycology study question set
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1. Fungi can be differentiated into two basic types based on the macroscopic appearance of their colonies. Describe the difference between molds and yeasts.
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a. Molds produce cottony, woolly, fluffy or powdery aerial growth above the culture medium. b. Yeasts produce opaque, creamy, or pasty colonies.
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2. If a fungus cultures can't be set up immediately, the best method(s) to preserve the specimen is to :
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b. Hold the specimen at room temperature c. Refrigerate the specimen
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3. India Ink preparation should be used to assist in the identification of:
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cryptococus neoformans
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4. What fungal media contains cycloheximide and/or chloramphenicol?
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mycosel
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5. What stain is used in the laboratory to help in the identification of molds?
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Lactophenol cotton blue
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6. Which media provides for optimal recovery of the more fastidious dimorphic fungi such as Blastomyces dermatiditis and Histoplasma capsulatum?
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sabhi agar
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7. Rhizopus and Absidia species both produce rhizoids. Describe the difference between the two species based on positioning of their rhizoids.
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Rhizoids of Rhizopus are derived from the hyphae immediately adjacent to the sporangiophores and are described as \"nodal\". Rhizoids of Absidia spp. are more delicate and are derived along the hyphae between the conidiophores, a derivation known as \"internodal\".
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Describe the microscopic appearance of Aspergillus spp. when observed using a Lactophenol Cotton Blue stain
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Aspergillus species are characterized by the production of uniform, 4-6 µm in diameter, hyaline, septate hyphae with parallel walls. A specialized segment , known as a foot cell, serves as the base of origin of the conidiophore. Conidiophores terminate in a swollen vesicle, from the surface of which are borne one (uniseriate) or two (biseriate) rows of phialides giving rise to chains of pigmented conidia.
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Which Aspergillus species has been responsible for the majority of serious infections?
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a. Aspergillus fumigatus
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Which of the following mold(s) is classified as a hyaline, filamentous mold producing conidia in chains? (May be more than 1 correct answer)
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a. Penicillium species b. Paecilomyces species c. Scopulariopsis species
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This mold has a unique characteristic of producing microconidia and macroconidia. Very key to its identification is the observation of long, sickle-form multicelled macroconidia separated by transverse septa. These macroconidia are sometimes described as \"canoes\".
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fusarium
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Scedosporium apiospermum (anamorphic form) is also known as
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Pseudallescheria boydii (sexual or telomorphic form).
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Dermatophytes generally infect what body sites ?
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Skin, hair and nails.
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This Dermatophyte is characterized by the production of clavate, smooth-walled, two- to four-celled macroconidia that are borne either singly from the hyphae, or more characteristically, in clusters of two or three. Very important in the identification of this mold is the absence of microconidia.
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epidermophyton floccosum
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How is dimorphism defined as it relates to fungi?
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The fungi exists in the environment (room temperature) as a mold, but as a yeast when incubated at 35-37ºC.
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How does Coccidiodes immitis microscopically present itself when grown at 30ºC using Lactophenol cotton blue stain?
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The hyphae are delicate and break up into barrel-shaped, arthroconidia that are separated by empty spaces (alternate staining).
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Alternaria spp, Curvularia spp. and Bipolaris spp. belong to a large group of rapidly growing saprophytic mold producing a melaninlike pigment resulting in darkly pigmented hyphae, visually recognized as dark gray or black colonies, both on the surface and reverse sides. What is the name of this group of fungi?
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dematiaceous fungi
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18. What is the purpose of cornmeal agar?
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Cornmeal agar is used for yeast morphology (pseudohyphae, true hyphae, blastoconidia, chlamydospores, etc).
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19. Candida albicans is germ tube (positive/negative); sucrose assimilation (positive/negative)?
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Germ tube=positive; Sucrose assimilation=positive.
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20. This yeast is innately resistant to fluconazole:
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c. Candida krusei
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21. This yeast presents with blastoconidia only, urease is positive, and portrays a pink, coral, red, or orange pigmentation. It often presents in the terminal stages of debilitated diseases.
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rhodotorula spp.
