SYSTEMIC AND OPPORTUNISTIC MYCOSES Flashcards
SYSTEMIC MYCOSES
● Blastomyces dermatitidis
● Paracoccidioides brasiliensis
● Coccidioides immitis
● Histoplasma capsulatum
Opportunistic Mycoses
a. Aspergillus spp
b. Fusarium spp.
c. Yeast (clinically significant)
i. Candida spp.
ii. Cryptococcus spp.
iii. Geotrichum spp
Causes North American Blastomycosis
Blastomyces dermatitidis
Human infection is initiated in the
lungs. Inhalation of the conidia or hyphal
fragments.
Blastomyces dermatitidis
Blastomyces dermatitidis specimens
sputum
pus
exudates
urine
biopsies from lesions
Delicate, septate hyphae with round or pyriform conidia borne slightly or directly on hyphae; resembling lollipops
Mold phase Blastomyces dermatitidis
Thick- walled, large yeast cells with single bud on broad-base; broad isthmus at constriction
Yeast phase Blastomyces dermatitidis
Microscopic Examination
Wet mounts of specimens
■ Show broadly attached buds on thick-walled yeast cells
Blastomyces dermatitidis
Blastomyces dermatitidis culture
Sabouraud’s agar or enriched blood agar at 30°C
Blastomyces dermatitidis treatment
amphotericin B.
Causes South American Blastomycosis. Inhaled, and initial lesions occur in the lung
Paracoccidioides brasiliensis
Most patients are 30-60 years of age, and over 90% are men.
Paracoccidioides brasiliensis
Paracoccidioides brasiliensis specimens
sputum, exudates, biopsies or other material from lesions
Small septate, branched hyphae with intercalary and terminal chlamydoconidia; few pyriform microconidia
Mold phase Paracoccidioides brasiliensis
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
Paracoccidioides brasiliensis
● Microscopic Examination
KOH or calcofluor white
■ Yeasts are often apparent
Paracoccidioides brasiliensis
Sabouraud’s agar or yeast extract agar
Paracoccidioides brasiliensis Most useful for diagnosis
Serologic Testing
Paracoccidioides brasiliensis treatment
Severe cases are treated with amphotericin B.
San Joaquin Valley Fever
Coccidioides immitis
Inhalation of arthroconidia leads to a primary infection. Major biologic hazard among laboratory personnel
Coccidioides immitis
Coccidioides immitis Specimens
sputum, exudate from cutaneous lesions, spinal fluid, blood, urine and tissue biopsies.
Coarse, septate, branched hyphae that produce thick-walled, barrel-shaped, rectangular arthroconidia that alternate with empty disjunctor cells.
Mold phase Coccidioides immitis
Large, round, thick-walled spherules with
endospores observed in tissue and direct
examination.
Yeast phase Coccidioides immitis
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
- Fungal stains: Gomori methenamine silver, periodic acid-Schiff or calcofluor white stain
- 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.
