SYSTEMIC AND OPPORTUNISTIC MYCOSES Flashcards by Khienja Maverick Gonzaga

SYSTEMIC MYCOSES

● Blastomyces dermatitidis
● Paracoccidioides brasiliensis
● Coccidioides immitis
● Histoplasma capsulatum

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Opportunistic Mycoses

a. Aspergillus spp
b. Fusarium spp.
c. Yeast (clinically significant)
i. Candida spp.
ii. Cryptococcus spp.
iii. Geotrichum spp

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Causes North American Blastomycosis

Blastomyces dermatitidis

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Human infection is initiated in the
lungs. Inhalation of the conidia or hyphal
fragments.

Blastomyces dermatitidis

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Blastomyces dermatitidis specimens

sputum
pus
exudates
urine
biopsies from lesions

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Delicate, septate hyphae with round or pyriform conidia borne slightly or directly on hyphae; resembling lollipops

Mold phase Blastomyces dermatitidis

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Thick- walled, large yeast cells with single bud on broad-base; broad isthmus at constriction

Yeast phase Blastomyces dermatitidis

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Microscopic Examination
Wet mounts of specimens
■ Show broadly attached buds on thick-walled yeast cells

Blastomyces dermatitidis

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Blastomyces dermatitidis culture

Sabouraud’s agar or enriched blood agar at 30°C

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Blastomyces dermatitidis treatment

amphotericin B.

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Causes South American Blastomycosis. Inhaled, and initial lesions occur in the lung

Paracoccidioides brasiliensis

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Most patients are 30-60 years of age, and over 90% are men.

Paracoccidioides brasiliensis

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Paracoccidioides brasiliensis specimens

sputum, exudates, biopsies or other material from lesions

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Small septate, branched hyphae with intercalary and terminal chlamydoconidia; few pyriform microconidia

Mold phase Paracoccidioides brasiliensis

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Large, round to oval, thick-walled yeast cells with multiple cuds which attach to mother cell by narrow constrictions resembles a ship wheel or pilot wheel or mariner’s wheel

Yeast phase Paracoccidioides brasiliensis

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Paracoccidioides brasiliensis
● Microscopic Examination

KOH or calcofluor white
■ Yeasts are often apparent

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Paracoccidioides brasiliensis

Sabouraud’s agar or yeast extract agar

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Paracoccidioides brasiliensis Most useful for diagnosis

Serologic Testing

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Paracoccidioides brasiliensis treatment

Severe cases are treated with amphotericin B.

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San Joaquin Valley Fever

Coccidioides immitis

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Inhalation of arthroconidia leads to a primary infection. Major biologic hazard among laboratory personnel

Coccidioides immitis

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Coccidioides immitis Specimens

sputum, exudate from cutaneous lesions, spinal fluid, blood, urine and tissue biopsies.

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Coarse, septate, branched hyphae that produce thick-walled, barrel-shaped, rectangular arthroconidia that alternate with empty disjunctor cells.

Mold phase Coccidioides immitis

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Large, round, thick-walled spherules with
endospores observed in tissue and direct
examination.

Yeast phase Coccidioides immitis

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Coccidioides immitis ● Microscopic Examination

KOH or calcofluor white stain: spherules and endospores

Coccidioides immitis Culture

Inhibitory mold agar, Sabouraud's agar, or blood agar slants

TRUE OR FALSE Coccidioides immitis Since arthroconidia are highly infectious, suspicious cultures are examined only in a biosafety cabinet.

TRUE

Identification must be confirmed by detection of C. immitis

specific antigen, animal inoculation or use of a specific DNA probe.

Darling’s disease/Spelunker’s disease

Histoplasma capsulatum

primary and begins in the lung and eventually invades the reticuloendothelial system.

Histoplasma capsulatum

most prevalent pulmonary infection in humans and animals

Histoplasma capsulatum

Initiated by inhalation of the conidia

Histoplasma capsulatum

Histoplasma capsulatum Specimens

sputum, urine, scrapings from superficial lesions, bone marrow aspirates and buffy coat blood cells.

Septate hyphae with round to pyriform microconidia on short branches or directly on hyphal stalk; later lage, round, thick-walled knobby, tuberculated macroconidia forms

Mold phase Histoplasma capsulatum

Small, budding, round to oval yeast cells; intracellular to mononuclear cells

Yeast phase Histoplasma capsulatum

Observe for small ovoid cells within macrophages

Histoplasma capsulatum

Histoplasma capsulatum culture:

glucose-cysteine blood agar at 37°C and on Sabouraud’s agar or inhibitory mold agar at 25–30°C

Fungal stains Histoplasma capsulatum

1. Fungal stains: Gomori methenamine silver, periodic acid-Schiff or calcofluor white stain 2. Giemsa-stained smears of bone marrow or blood

Clinically Significant YEASTS

● Candida spp. ● Cryptococcus spp. ● Geotrichum spp.

Most important group of opportunistic fungi pathogens

Candida spp.

Normal flora of the skin, mucous membranes and gastrointestinal tract. Capable of causing Candidiasis

Candida spp.

species exist as oval, yeastlike forms that produce buds or blastoconidia

Candida

Produce pseudohyphae and true hyphae except C. glabrata

Candida spp.

Candida spp. specimens

Swabs and scraping from superficial lesions, blood, spinal fluid, tissue biopsies, urine, exudates, and material from removed intravenous catheters.

Gram-stained smears or histopathological slides for tissue biopsies, centrifuged spinal fluid, and other specimens ■ Pseudohyphae and budding cells

Candida spp.

Skin or nail scrapings are first placed in a drop of 10% KOH and calcofluor white

Candida spp.

All specimens are cultured on fungal or bacteriologic media at room temperature or at 37°C. Special agar for Candida is CHROM Agar

Candida spp.

Candida spp. in CHROM Agar Light green colonies

C. albicans

Dark-violet / dark mauve colonies

C. glabrata

Dark green colonies

C. dubliniensis

Pink , purple. May exhibit multiple color

C. auris

Fuzzy pale pink

C. krusei

Metallic/ dull-blue/ grayish blue

C. tropicalis

Pink to purple colonies/ Pink-lavender colonies

C. kefyr

Most isolated species from clinical material

Candida albicans

Can be saprophytic in oral cavities, Gi or vaginal tract. Causes candidiasis or moniliasis infection

Candida albicans

Oral moniliasis. Oral Thrush (white stuff/white cottage-cheese like patches on the mouth)

Candida albicans

Vaginal moniliasis Vulvovaginitis, Onychomycosis (nail infections) and Paronychomycosis (cuticle infections)

Candida albicans

hyphae-like extensions of young yeast cells showing parallel sides, aseptate and will not constrict at their point of origin

Germ-tube Candida albicans

look like germ tubes but are aseptate and constricted at their point of origin.

Pseudohyphae Candida albicans

This usually causes meningitis in patients with AIDS

Cryptococcus neoformans

Encapsulated yeast cell in bird and bat droppings; “pigeon droppings”

Cryptococcus neoformans

Torulosis/Torulopsis or European Blastomycosis

Cryptococcus neoformans

Specimens include cerebrospinal fluid, tissue, exudates, sputum, blood, cutaneous scrapings, and urine.

Cryptococcus neoformans

Specimens are often examined in wet mounts, both directly and after mixing with India ink.

Cryptococcus neoformans

Alternatively, on an appropriate diphenolic substrate, the phenol oxidase of C. neoformans produces melanin in the cell walls and colonies develop a

brown pigment.

Often initially appears as a white to cream-colored, yeastlike colony; some isolates may appear as white, powdery molds.

Geotrichum candidum

Hyphae are septate and produce numerous rectangular to cylindrical to barrel-shaped arthroconidia.

Geotrichum candidum

Clinically Significant OPPORTUNISTIC MYCOSES

● Aspergillus spp. ● Fusarium spp.

Can cause disease by ingestion of mycotoxins, traumatic inoculation, or inhalation.

Aspergillus spp.

Also capable of causing disseminated infection in immunocompromised patients, pulmonary or sinus fungus ball, allergic bronchopulmonary aspergillosis, external otomycosis, mycotic keratitis, onychomycosis, sinusitis, endocarditis and central nervous system infection.

Aspergillus spp.

The species are identified according to morphologic differences in their structures.

Aspergillus spp.

Aspergillus spp. specimens

sputum, other respiratory tract specimens and lung biopsy tissue.

Rapidly growing mold that produces a fluffy to granular, white to blue-green colony.

Aspergillus fumigatus

Characterized by the presence of septate hyphae and short or long conidiophores with a characteristic “foot cell” at their base.

Aspergillus fumigatus

Cultures of A. fumigatus are thermotolerant___and able to withstand temperatures ___

thermotolerant up to 45°C

Somewhat more rapidly growing species that produces yellow-green colony.

Aspergillus flavus

conidiophore is coarsely roughened near the vesicle.

A. flavus

Produces darkly pigmented, roughened spores macroscopically, but microscopically its hyphae are hyaline and septate.

Aspergillus niger

Produces colonies within 2 to 6 days. Growth begins initially as yellow colony

Aspergillus niger

With age, the colony becomes jet black and powdery, but the reverse remains buff or cream colores.

Aspergillus niger

Less commonly seen in the clinical laboratory

Aspergillus terreus

Produces tan colonies that resembles cinnamon.

Aspergillus terreus

Produces larger cells, aleurioconidia, which are found on submerged hyphae.

Aspergillus terreus

Most commonly isolated organisms within this group are within the Fusarium solani species complex.

Fusarium spp.

Long been known to cause mycotic keratitis.

Fusarium spp.

Oftentimes infections are associated with the consumption of grains contaminated with trichothecene mycotoxins produced by F. sporotrichiodes or F. poae.

Fusarium spp.

Capable of causing sinusitis, wound (burn) infection, allergic fungal sinusitis, endopthalmitis, and disseminated fusariosis.

Fusarium spp.

Colonies grow rapidly, within 2 to 5 days, and are fluffy to cottony and may be pink, purple, yellow, green or other colors, depending on the species.

Fusarium spp.

Most common medium used to induce sporulation is of Fusarium spp.

corneal agar.

Fusarium spp. keys to identification are based on growth on

potato dextrose agar.