Mycology Systemic Dimorphic Fungi Division of Medical Technology Carol Larson MSEd, MT(ASCP) Please click audio icon to hear Carol’s narration
Dec 21, 2015
MycologySystemic Dimorphic Fungi
Division of Medical Technology
Carol Larson MSEd, MT(ASCP)
Please click audio iconto hear Carol’s narration
General Characteristics
• Growth rate: 2-4 weeks
• Identification– Direct specimen examination– Colony morphology– Microscopic morphology– Definitive diagnosis is prove dimorphism
• Mycelial stage at 25-30ºC• Yeast / spherule stage in host at 35-37ºC
Click icon for audioSystemic Dimorphic Fungi
Epidemiology
• Primarily in North America or South America
• Found in:– Soil– Decaying vegetation– Bird droppings– Bat droppings
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Clinical Significance
• Pathogens
• Man incidental host
• Acquire by inhalation
• Develop respiratory infection
• Can disseminate and become systemic infection
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Clinical Significance
• Histoplasmosis– Histoplasma capsulatum
• Blastomycosis– Blastomyces dermatitidis
• Coccidioidomycosis– Coccidioides immitis
• Paracoccidioimycosis– Paracoccidioides brasiliensis
Click icon for audioSystemic Dimorphic Fungi
For the systemic dimorphic fungi, what must be demonstrated in the lab to definitively identify them?
The systemic dimorphic fungi have two forms (mold and yeast/spherule) and both must be seen in the laboratory either in culture or in direct examination of a specimen.
How are the systemic dimorphic fungal infections acquired?
By inhalation of the conidia and fungal elements. The infection begins in the lungs for all of the systemic dimorphic fungi.
Histoplasmosis
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• Histoplasma capsulatum
• Pathogenesis– 95% of cases are asymptomatic– Infection begins in lung– Invades reticuloendothelial system– Can disseminate (especially in
immunocompromised patients)
Laboratory Diagnosis
• Specimen– Sputum– Blood– Bone marrow– Urine– Oral lesion scraping– Lymph node biopsy– Liver
Click icon for audioHistoplasmosis
Laboratory Diagnosis
• Direct detection methods– Giemsa or Wright’s stains– Calcofluor white stain, histological stains– Look for small intracellular yeast cells
Click icon for audioHistoplasmosis
Mold - Histoplasma capsulatum
Click icon for audioHistoplasmosis
• Media– Sab’s and Inhibitory Mold agars
• Good growth at 2-4 weeks
– Mycosel agar – no growth
• Incubate– 25-30ºC– Ambient air– Up to 4-6 weeks
Yeast - Histoplasma capsulatum
• Media– Blood enriched media– Incubate at 35ºC in ambient air for 2-4 weeks
• Colony morphology
• Microscopicmorphology
Click icon for audioHistoplasmosis
What is the diagnostic form for Histoplasma capsulatum and what does it look like?
The mold phase – its macroconidia are large, round, unicellular, thick-walled and tuberculated.
In patient specimens, where is a common place that you would find Histoplasma capsulatum yeast?
Histoplasma capsulatum yeast cells are often found intracellular in mono-nucleated cells.
Blastomycosis
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• Blastomyces dermatitidis
• Pathogenesis– Acute or chronic suppurative and
granulomatous infection– Infection begins in lung– Can disseminate to lungs, bone, soft
tissue and skin
Laboratory Diagnosis
• Specimen– Cutaneous lesions– Sputum– Biopsy of affected organ
Click icon for audioBlastomycosis
Laboratory Diagnosis
• Direct detection methods– KOH prep– Histological stains– Look for large
spherical budding yeast with single bud connected to parent cell by a broad base
Click icon for audioBlastomycosis
Mold - Blastomyces dermatitidis
Click icon for audioBlastomycosis
• Media– Sab’s and Inhibitory Mold agars
• Good growth at 1-4 weeks
– Mycosel agar – no growth
• Incubate– 25-30ºC– Ambient air– Up to 4-6 weeks
Mold - Blastomyces dermatitidis
• Colony morphology
• Microscopic morphology
Click icon for audioBlastomycosis
Yeast - Blastomyces dermatitidis
• Media– Cottonseed conversion agar– Incubate at 35ºC in ambient air for 1 week
• Colony morphology
Click icon for audioBlastomycosis
Yeast - Blastomyces dermatitidis
• Microscopic morphology
Broad-Based Budding yeast
Click icon for audioBlastomycosis
Other Test Methods
• Exoantigen test– Immunodiffusion
• Nucleic acid amplification assay
Click icon for audioBlastomycosis
What is the diagnostic form for Blastomyces dermatitidis and what does it look like?
The yeast phase – it has a broad based single bud and is large in size.
Describe the appearance of the mold form of Blastomyces dermatitidis?
The mold form of Blastomyces is very nondescript. It has hyaline, septate hyphae. The conidiophores are short and unbranched and the conidia are hyaline, pyriform, unicellular, terminal, and solitary.
Coccidioidomycosis
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• Coccidioides immitis
• Pathogenesis– 60% of infections are asymptomatic– Infection begins in lung– Can disseminate (1%)– Southwest U.S. desert area (endemic to
San Joaquin Valley)
Laboratory Diagnosis
• Specimen– Sputum– Biopsy of affected organ
Click icon for audioCoccidioidomycosis
Laboratory Diagnosis
• Direct detection methods– KOH prep, Calcofluor white stain– Histological stains– Look for spherule– No yeast form
Click icon for audioCoccidioidomycosis
Mold - Coccidioides immitis
Click icon for audioCoccidioidomycosis
• BIOHAZARD to lab personnel
• Media– BAP, Sab’s, Inhibitory Mold, and Mycosel
• Good growth at 3 days to 3 weeks
• Incubate– 25-30ºC– Ambient air– Up to 4 weeks
Spherule - Coccidioides immitis
• Not recommended
• Media– Special media incubated at 42ºC
• Can infect lab animals and do tissue biopsy (experimental)
Click icon for audioCoccidioidomycosis
Other Test Methods
• Exoantigen test– Immunodiffusion
• Nucleic acid amplification assay
Click icon for audioCoccidioidomycosis
What form for Coccidioides immitis is found in patient specimens?
The spherule. There is no yeast phase for this fungus.
What does Coccidioides immitis look like when cultured on SAB agar that has been incubated at 30°C?
Barrel-shaped alternating arthroconidia.
Paracoccidioidomycosis
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• Paracoccidioides brasiliensis
• Pathogenesis– Infection begins in lung– Can be asymptomatic and then
disseminate to nasal and oral mucosa, gingivae, or conjunctivae
– South America (South American Blastomycosis)
Laboratory Diagnosis
• Specimen– Sputum– Biopsy of affected organ
Click icon for audioParacoccidioimycosis
Laboratory Diagnosis
• Direct detection methods– KOH prep, Calcofluor white stain, and
Histological stains– Look for large
round or oval, multiple budding yeast cells (“mariner’s wheel”)
Click icon for audioParacoccidioimycosis
Mold - Paracoccidioides brasiliensis
Click icon for audioParacoccidioimycosis
• Media– Sab’s and Inhibitory Mold agars
• Good growth at 3-4 weeks
– Mycosel agar – no growth
• Incubate– 25-30ºC– Ambient air– Up to 4-6 weeks
• Colony morphology
• Microscopic morphology
Click icon for audioParacoccidioimycosis
Mold - Paracoccidioides brasiliensis
• Media– Blood enriched media– Incubate at 35ºC in ambient air for 4 weeks
• Colony morphology
• Microscopic morphology
Click icon for audioParacoccidioimycosis
Yeast - Paracoccidioides brasiliensis
What is the diagnostic form for Paracoccidioides brasiliensis and what does it look like?
The yeast form appears as a large multiple budding yeast that looks like a mariner’s wheel.
In Summary …
• Diseases– All begin infection in lungs– Disseminate
• Identification– Demonstrate dimorphism– Direct specimen exam– Culture (mold and yeast forms)– Other testing
Systemic Dimorphic FungiClick icon for audio