Fungus in Tissue Brief Review Margie Morgan, PhD D(ABMM)

1. Fungus in Tissue
Brief Review
Margie Morgan, PhD D(ABMM)
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2. Important Infections with Molds and Yeast
• Hyaline septate molds Yeast
• Aspergillus species Candida
• Pseudallescheria (Scedosporium) complex Cryptococcus
• Fusarium species
• Hyaline aseptate molds (mucormycetes)
• Dimorphic fungi
• Histoplasma capsulatum
• Coccidioides immitis and C. posadasii
• Blastomyces dermatitidis
• Sporothrix schenckii complex
• Penicillium (Talaromyces) marneffei
• Dematiacious molds
• Mycetoma
• Chromoblastomycosis
• Phaeohyphomycosis
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3. Hyaline Septate Molds
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4. Aspergillus Species in tissue
Dichotomous = branching
into two pieces
Higher magnification
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5. Aspergillus compared to Mucormycete fungi (Mucor)
Broad hyphae rare/no septations
Broader hyphae than Aspergillus
Branching more irregular/some
at 90* angle
Thinner hyphae than Mucormycete
Regular septations, 45* angle
branching referred to as dichotomous
branching
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6. Aspergillus and
Pseudallescheria(Scedosporium)
Aspergillus hyphae is usually broader than Scedosporium species
Both show dichotomous branching, invade vessels, and have similar infections.
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7. Aspergillus
fumigatus
Fungus ball
Culture
30*C / 4 days
Scotch Tape
Prep
A. fumigatus is the most
common Aspergillus
species to cause
pulmonary or
disseminated infection
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8. Aspergillus fumigatus
Aspergilloma formation in the lung
fungus ball
Invasion of blood vessels
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9. Aspergillus niger
Unusual to cause
pulmonary infection,
most often associated
with ear infections
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10. Aspergillus
terreus
Note:
Intrinsic resistance to
amphotericin
Can disseminate and
cause disease much like
Aspergillus fumigatus
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11. Aspergillus
flavus
Can cause infection
much like Aspergillus
fumigatus
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12. Fusarium species
Random branching
of hyphae / no
characteristic pattern
Hyaline septate with banana
shaped conidia
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13. Mucormycetes –
Mucor and Rhizopus
Broad ribbon like hyphae
without septations – can
appear faintly staining
Rhizopus
Mucor
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14. Dimorphic Molds
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15. Blastomyces dermatitidis
No color (negative) on
Mucicarmine stain
stain S
lung
lung
Skin is a primary site of
dissemination
GMS
PAS
Dermis
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16. Blastomyces dermatitidis Culture
Scotch tape prep
Growth 30* C
In @ 2-3 weeks
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17. Coccidioides immitis
and C. posadasii
Spherule formation in human tissue/ NO yeast forms
Spherules
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18. Coccidioides species
Mold growth in 3-5 days at 30*C
Alternating barreled
arthroconidia
Scotch tape preparation
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19. Histoplasma capsulatum Bone marrow
lung
Yeast are usually
intracellular within
macrophages,
2-4 um in size
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20. Histoplasma
capsulatum
In fixed tissue, P. brasiliensis forms multiple
buds on the primary yeast cell, appears similar
to macroconidia of Histoplasma
H. capsulatum
adhesive tape prep
Tuberuculate macroconidia
microconidia
**Do not confuse Histoplasma
mold phase with the yeast of
Paracoccidioides brasiliensis
complex in fixed tissue
Growth in culture
30* C for 2 weeks
Yeast of P. brasiliensis in
fixed tissue
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21. Sporothrix schenckii
Dermis
inflammation
Yeast cells
variable in
shaper some
Cigar shaped
Asteroid body commonly
the only structure observed
Progression up lymphatics
Adhesive tape preparation /spores
form daisy head arrangement
Culture at 30* C
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22. Penicillium (Talaromyces)
marneffei
Skin – yeast like cells
Bone
marrow
30*C culture/ note red
diffusible pigment
surrounding green colony
Adhesive prep
of mold
Skin lesions
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23. Dematiacious (Black) Molds
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24. Subcutaneous fungal infections
• Infection with dematiaceous (black) molds
• Chromoblastomycosis
• Phaeohyphomycoses
• Infection with dematiaceous (black) molds or
higher bacteria (Nocardia)
• Mycetoma
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25. Chromoblastomycosis
Cauliflower (raised)
skin lesions
Naturally brown colored copper
penny or sclerotic body identified
in tissue
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26. Phaeohyphomycosis
GMS
H & E stain
Naturally brown colored hyphae in tissue
Nodular skin lesions
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27. Mycetoma
Sulfur
granule
Actinomycotic Mycetoma Eumycotic Mycetoma
Nocardia species Black (dematiacious) molds
Sulfur granule formed in tissue Sulfur granule formed in tissue
with thin filamentous bacteria with thick dark hyphae
Swollen extremity
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28. Candida species
GI tissue
C. Albicans
pseudophyphae extensions
growing out from colony
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29. Cryptococcus species
Yeast are round and
variable in size (2-20um)
with capsule.
Capsule stains dark pink
on mucicarmine stain
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