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82 Cards in this Set
- Front
- Back
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Define superficial mycoses
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Infections caused by fungi that colonize the keratinized outermost layers of the skin, hair, and nails. Infections are generally asymptomatic, nondestructive, and stimulate little or no host immune response
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What causes Pityriasis versicolor
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Malassezia furfur infection
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What are the three common dermatophytes
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Epidermophyton, Microsporum, Trichophyton
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What are the six common Dermatophytic tinea infections
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Tinea capitis (head)
Tinea pedia (foot) Tinea cruris (groin) Tinea barbae (beard) Tinea corporus (body) Tinea unguium=onychomycosis (nails) |
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How are dermatophytes infections diagnosed
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Dissolve skin scrapings in KOH to digest keratin. Microscopic exam will reveal branched hyphae
Direct exam of hair and skin with Wood's light (UV 365nm). Microsporum audouinii will fluoresce. |
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What are some general characteristics of subcutaneous mycoses
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Usually introduced by trauma; fungi usually found in soil; Involve dermis, subcutaneous tissue, and bone
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How does sporotrichosis (Sporothrix schenckii) present
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Boil-like bumps moving along lymphatic system, develop into open sores.
Yeast form found in lesions. |
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What is Chromoblastomycosis
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Cauliflower-like crusted nodules on skin, sclerotic bodies.
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What is phaeohyphomycosis
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A disease caused by dematiaceous molds
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What is a Mycetoma
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Draining abscesses, granules present in abscess. Usually on hands and feet.
Introduced by traumatic injury. |
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What is thallic conidogeny
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Septum of hyphae forms first, then separation.
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What are chlamydospores
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The chlamydoconidia of yeast
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What is distinct morphologically about zygomycota (3 things)
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Aseptate hyphae.
Spores are enclosed in a sac (sporangium) at end of a stalk (sporangiophore). Sexual structure is zygospore. |
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What are the major groups of fungi?
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Zygomycota, Imperfect, Ascomycota, Basidiomycota
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Two traits common to all fungi
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Chitin in cell wall and ergosterol in cell membrane
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What are the sexual and asexual reproductive structures called
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Sexual = Spores
Asexual = Conidia |
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What is a "rapid" growth rate vs. a "yeast-like" growth rate
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Rapid = ~5 days
Yeast = 2 days |
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What is the most common cause of fungal meningitis
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Cryptococcus neoformans
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Dimorphic fungi: yeast form temperature and mold form temperature
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Yeast = 37
Mold = 25 |
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What is the difference between a germ tube and a pseudohyphae
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Pseudohyphae is "pinched in" where it joins the bud.
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What are the zygomycota and what is their fwd/rev coloration?
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Rhizopus, Absidia, Mucor, Syncephalastrum.
Cottony lid lifter, white/brown fwd and rev. |
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How are the zygomycota differentiated from one another?
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Rhizopus = vertical rhizoids
Mucor = no rhizoids Absidia = separae/far/side rhizoids Syncephalastrum = daisy-head. |
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What are the dematiaceous molds?
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Alternaria and Curvularia.
Dark pigmented on both sides. |
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The conidia of Alternaria are:
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Club shaped poroconidia; muriform (transverse and longitudinal lines).
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The conidia of Curvularia are:
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Cresent-roll shaped; parallel lines only; central cell is largest.
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What are the hyaline molds?
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Fusarium and Acremonium
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What is distinctive about Fusarim?
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Pink or purple colonies.
Canoe-shaped macro and micro conidia; "foot cell". |
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Describe the microscopic appearance of Acremonium:
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Long, tapering phialid with cluster of small conidia which disseminate under the microscope.
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The fwd/rev colors of the dermatophytes are:
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White/tan surface
Distinctive reverse |
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All opportunistic fungi have what growth rate?
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Rapid
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Dermatophytes have what growth rate and all infect what tissue type?
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Intermediate
Skin |
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Epidermophyton infects which cutaneous tissues?
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Skin, Nails
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Microsporum infects which cutaneous tissues?
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Skin, Hair
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Trichophyton infects which cutaneous tissues?
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Skin, Hair, Nails
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What is a Geophilic organism?
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Organism that normally inhabits soil
(eg. Microsporum gypseum) |
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What is a zoophilic organism?
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Organism that is primarily parasitic to animals
(eg. Microsporum canis) |
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What is an anthropophilic organism?
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Organism that is primarily parasitic to humans
(eg. Trichophyton rubrum and Epidermophyton floccosum) |
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What species will fluoresce under a Wood's Lamp?
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Microsporum audouinii
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Describe the micro and macro conidia of Epidermophyton:
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No microconidia
Few smooth, thin-walled macroconidia |
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Describe the micro and macro conidia of Microsporum:
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Thick, rough macroconidia
Rare microconidia |
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Describe the micro and macro conidia of Trichophyton:
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Many microconidia
Rare macroconidia |
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How does Dermatophyte Test Medium work?
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Closed tube with phenol red indicator; change to red color is positive.
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What method is used to speciate Trichophyton?
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Sequencing, because the 7 agars is too difficult/time consuming and they all look the same.
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What is distinctive about Trichophyton rubrum?
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Deep red reverse color.
Most common dermatophyte. |
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What is distinctive about Trichophyton tonsurans?
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Diffusing reddish-brown reverse.
Hair perforation positive. |
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What is distinctive about Microsporum audouinii?
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The one slow grower
Bizarre hypahe Wood's Lamp positive |
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What is distinctive about Microsporum canis?
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Deep yellow reverse
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What is distinctive about Microsporum gypseum
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Geophilic
Yellow/orange/red reverse |
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What is distinctive about Malassezia furfur?
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Requires lipid to grow in culture (olive oil).
Is a yeast. |
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What is the difference between Scedosporium apiospermum and Pseudallescheria boydii?
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Scedosporium = Asexual
Pseudallescheria = Sexual |
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List the subcutaneous fungal pathogens (5):
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Sporothrix schenckii
Phialophora verrucosa Exophiala Jeanselmei Cladosporium Carrionii Pseudallescheria boydii/Scedosporium apiospermum |
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List the systemic mycoses (4):
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Histoplasma capsulatum
Blastomyces dermatitidis Coccidiodes immitis Sporothrix schenckii |
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What is Actinomycetes?
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A fungus-like bacteria.
Cell wall contains mycolic acid. Grows on fungal media. |
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What is used to dissolve keratin in samples?
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10% KOH
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What urine sample should be used for detecting a fungal infection?
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First morning
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What should be used on a respiratory sample?
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NALC (N-acetyl-L-cystein)
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How is a CSF sample tested for fungus?
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Centrifuged and observed directly
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Explain the lactophenol cotton blue stain:
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Phenol: Kills any organisms
Lactic acid: Preserves fungal structures Cotton blue: Stains chitin |
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Explain Calcoflour White stain:
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Stains chitin
Requires special scope (epiflourescent) |
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What temperature should agars be incubated at?
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37 if testing for yeast.
25-30 if mold. |
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What is unique about Sabourand Dextrose Agar
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The pH is altered to 8.8-7.0 (body pH).
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What media is Candida albicans grown on and what do you look for?
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Cornmeal Tween 80.
Look for terminal chylamydospores. |
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What do you grow on Brain-Heart infusion agar?
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Organisms that are difficult to grow, such as systemics.
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When growing a suspected fungal organism on a plate, how many plate sets are needed and why?
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One set with and one without antibiotics, to get a full range of identification methods.
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What organism looks the same grown at 30 and 37 degrees, forming arthroconidia?
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Coccidiodes.
Only systemic that looks the same at both temperatures. |
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What does mold inhibitory agar have?
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Gentomycin
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When is potato dextrose agar used? Why?
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When making a slide culture, because it helps preserve better.
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What is added to a dermatophyte-containing skin scraping before visualizing?
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KOH, to dissolve the human cells.
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What are the three dermatophytes? How are they differentiated?
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Trichophyton
Microsporum Epidermophyton Differentiated based on presence/absence of macro/microconidia. |
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Describe the microscopic appearance of Epidermophyton:
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Only macroconidia
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Yeast grow on what medium?
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Blood agar plates (look like bacteria)
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Yeasts gram stain positive or negative?
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Positive
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Opportunistics grow at what speed?
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Rapid
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How do most fungi get into the body?
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Respiratory
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Aspergillus fumigatus has what front color?
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Blue-green
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Aspergillus flavus has what front color?
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Yellow-green
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Penicillium marneffi causes what disease? Why does it cause this?
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Disseminated penicillosis.
It is dimorphic. |
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What is the characteristic color of Penicillium marneffi?
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Diffusing red pigment
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List the cutaneous fungi (2):
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Dermatophytes (microsporum, trichophyton, epidermophyton).
Malasezia furfur. |
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When grown on a plate, the sexual or asexual found will always be found?
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Asexual
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Systemic fungi are endemic where? What organism is the exception?
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Arid southwest U.S.
Coccidiodes |
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For what group of organisms is only the reverse color distinctive?
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Dermatophytes
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