5. Dematiaceous Fungi
General characteristics:
• Large group of rapidly growing
saprotrophic molds producing a
melanin like pigment resulting in
darkly pigmented hyphae visually
recognized as dark grey or black
colonies both on the obverse & the
reverse side.
6. • Ubiquitous in nature, exist as saprotrophes.
• Humans & animals serve as accidental
hosts after traumatic inoculation of
organism into cutaneous & subcutaneous
tissue.
• Infections range from mild, hardly
noticeable cutaneous infections to fatal
brain diseases in otherwise healthy
individuals.
7. Virulence Factor Clinical Significance
• Presence of melanin in cell walls, is
believed to be a major virulence
factor.
- It gives protection against
solar irradiation.
• Diseases by melanized fungi are rare,
they are significant because of their
occurrence in otherwise healthy
individuals, and no notable increase in
their frequency is noticed with the
emergence of immunocompromised
hospital populations.
8. Microscopically
• Dark yellow brown mycelium composed of
uniform hyphae with parallel walls, having
true septate hyphae.
• Cell wall contain melanin like compound
making hyphae darkly pigmented.
• Darkly stained macrconidia.
• In H/P sections these pigments may be
accentuated by Fontanna masson stain.
10. Genera of Medical Importance Include
Mycetoma
White grain
•P. boydii
•Acremonium
•Fusarium
Black grain
•Madurella
mycetomatis
•Exophiala
jeanselmei
•Fonsecaea
spp.
Chromoblastomycosis
Cladosporium
Phialophora
Fonsecaea
spp.
Phaeohyphomycosis
E. jeanselmei
Exophiala
dermatitidis
Curvularia
Bipolaris
Alternaria
Exserohilum
spp.
Sinusitis
Alternaria
Bipolaris
Exserohilum
Curvularia
Mycotic Keratitis &
Endophthalmitis
E.
dermatitidis
Bipolaris
Curvularia
spp.
Brain abscess
Cladophialoph
ora bantiana
E.
dermatitidis
Bipolaris spp.
11. Superficial Infections
Tinea Nigra (Hortae werncekii)
• Superficial skin infection.
• Brownish black, non-scaly, macular patches.
• Centrifugal extension, darkest at periphery.
• Palms (tinea nigra palmaris) & sole (tinea nigra
plantaris).
- H. werneckii- halophilic saprotrophe.
- Hyper-hydrotic individuals.
• D/D: 1. Benign nevus.
2. Malignant melanoma.
3. Pityriasis versicolor.
Tinea nigra
Acral lentiginous melanoma
Pityriasis versicolor
12. Superficial Infections (cont)
Black Piedra (Piedraia hortae)
• Tinea Nodosa.
• Primarily occur in tropical areas.
• Nodular type infection of hair shaft (scalp).
• Starts under the cuticle, grow outside & envelope hair
shaft, penetrate cortex.
• Gritty hard, brown-black nodules, firmly attached to
hair shaft, metallic sound while combing.
• Nodules: spores embedded in cement-like substance
or branched hyphae with asci.
• D/D: 1. Nits of pediculosis.
2. Tinea capitis.
Black piedra
Nits of pediculosis
Tinea capitis
13. The recent DNA sequence data indicate that nearly all etiological
agents of Phaeohyphomycosis, Chromoblastomycosis and Phaeoid
taxa of Eumycetoma belong to a single clade of
Loculoascomycetes fungi.
15. Mycetoma
Eumycotic
Bacterial
Black grain
White grain
Actinomycotic
• Chronic Granulomatous infection of
subcutaneous tissue.
• Triad: Tumefaction,
Multiple draining sinsuses,
Granules in discharge.
• Swelling, purplish discoloration, serous or
serosanguineous discharge.
• Mostly Lower extremities (any part).
16. • Progressive destruction- bone, muscle other tissues,
requires amputation.
• Mostly occurs tropical region but can occur in temperate
zone.
Multiple draining sinuses Lytic bone lesions on X-ray
17. Chromoblastomycosis
• Chromoblastomycosis is cutaneous & S/C infection
characterized by formation of polymorphic, verrucoid,
crusted or ulcerated lesions.
• Characteristic Sclerotic Bodies present.
- muriform cells (ideal).
- medlar bodies.
- copper-penny bodies.
- intermediate vegetative state b/w yeats
and hyphae.
• Papule slowly spreads to form warty or tumor like
lesion (cauliflower like growth).
• Dorsal surface of feet & legs, may involve head &
neck.
• Widely distributed mostly in tropical and subtropical
areas.
18. • These infections cause hyperplasia (PEH) of the
epidermis of the skin, which may be mistaken
for squamous cell carcinoma.
Characteristic black dots Mimicking SCC
20. Phaeohyphomycosis
• Greek Phaeo = dusky, gray.
• Concept of “phaeohyphomycosis’’ was 1st proposed by Ajello et al in 1986 to “cover
all infections of cutaneous, subcutaneous, & systemic nature caused by
hyphomycetous fungi that develop in host tissues in the form of dark walled,
dematiaceous, septate mycelial elements.
• Characterized by multiple stellate abscesses, progress to circumscribed lesion with
central cavity filled with pus and surrounding fibrous wall.
• Phaeohyphomycosis applies to several clinical entities :
1. Phaeohyphomycotic cysts
2. Sinusitis
3. Keratitis
4. Endocarditis
5. Pneumonia
6. Brain abscess
7. Systemic infections.
25. Ring infiltrate in a case of keratitis caused by
dematiaceous fungi
Corneal picture of a case of dematiaceous fungal keratitis
presented as peripheral ulcerative keratitis
27. A common theme in Laboratory diagnosis:
Sample collection:
• Superficial infections: Hair nodules (Black Piedra), skin scrapings
and biopsy (Tinea Nigra).
• Subcutaneous infections: Grains (Mycetoma), skin scrapings with
black dots or biopsy specimen (Chromoblastomycosis).
• Systemic infections: Aspirates from cysts, curretings from
plaques, nodules and drained abscesses (Phaeohyphomycosis).
Direct examination: KOH Mount (20%)- morphology of hyphae.
Culture: SDA with antibiotics- colony characteristics.
28. Superficial Infection
Tinea Nigra
Hortaea werneckii
Grows slowly, 2- 3 weeks.
Colony morphology: Tar black, smooth, slimy
& glistening, yeast- like.
Microscopically: Hyphae are wide, densely
septate (at maturation), becoming
dark brown & thick walled.
Conidia are produced by
annellophores, bear successive
rings (annellids)
29. Superficial Infection (cont)
Black Piedra
Piedraia hortae
Grows slowly.
Colony morphology: small, folded, velvety and
dark brown to black in color.
reddish brown diffusible pigment
(obverse) black in color (reverse).
Microscopically: Septate hyphae, ascostromata,
asci, and ascospores are visualized.
Hyphae are darkly pigmented.
30. Superficial Infection (cont)
(a) 10% potassium hydroxide (KOH) examination of black colored nodule
shows a concretion forming a collar around hair shaft. Concretions are
made up of filamentous hyphae, held together in a mass by cement like
substance. Spores are seen at the edges of the nodule (←), (b) KOH
mount of crushed nodule shows brown dematiaceous closely septate
hyphae (H) with few chlamydospores (Ch). (c) Culture on Sabouraud's
dextrose agar shows small, compact, blackish conical colonies with
velvety surface. (d) Microscopic examination of the colonies showing
round, dark brown, globus ascus (→) with ascospores.
31. White Grain Mycetoma
P. Boydii
Grows rapidly.
Initial growth- white fluffy colony,
mousy gray in several weeks
A. falciforme
Grows slowly.
Produce gray brown colonies.
32. Black Grain Mycetoma
M. mycetomatis
Grows slowly.
Colony morphology: White to olive brown.
Brown diffusible pigment (characteristic).
Microscopically: SDA: Moniliform septate hyphae with Chlamydospores.
CMA: short pointed conidiophores, conidia at tips of
flask-shaped phialides.
33. Black Grain Mycetoma
E. jeanselmei
Grows slowly.
Colony morphology: Yeast-like and darkly pigmented
olive to black velvety appearance
with the production of aerial
hypha.
Microscopically: Daughter cells are produced by
annellides rather than true bud
Conidiophores are cylindrical and have a
tapered tip.
Annellations may be visible at the tip.
Clusters of oval to round conidia are
apparent.
34. Identification of
Chromoblastomycosis
KOH Mount: Sclerotic bodies (rounded, brown, 4 to 10 μm
in diameter and resemble “copper pennies”).
Macroscopically: Heaped up colonies.
Darkly pigmented.
Gray to Olive Black & Velvety.
Reverse side of colony is jet black.
Microscopic examination is necessary for definitive
identification.
Sclerotic bodies
35. Cladosporium spp.
Microscopically: Long chains of elliptical conidia
(blastoconidia).
Borne from erect, tall, branching
conidiophores.
Dysjunctor & shield cells.
36. Phialophora spp.
Phialophora verrucosa:
Microscopically: Phialides with a distinct cup or
flask-shaped collarette.
P. richardsiae:
Microscopically: Produces phialides with a flattened
or saucer-like collarette .
Conidia are produced endogenously and occur in
clusters at the tip of the phialide.
37. Fonsecaea spp.
Microscopically: Conidial heads with
sympodial arrangement of conidia, with
primary conidia giving rise to secondary
conidia.
• Cladosporium type.
• Phialophora type.
• Rhinocladiella type.
Rhinocladiella type of sporulation:
Single-celled conidia are produced on
denticles that arise from all sides of
conidiophores (sympodially).
40. Alternaria spp.
Microscopically: Hyphae are septate & golden
brown pigmented.
Conidiophore: Simple, sometimes branched.
Short chains of large, brown, smooth
walled, multicelled macroconidia.
Shaped like drumsticks with elongated
beak of one conidium butting against
the rounded blunt end of next.
42. Stemphylum spp.
Microscopically: Muriform macroconidia similar to
that of Ulocladium.
Borne singly at the apex of a short,
straight non geniculate conidiophore
Macroconidia are swollen & rounded at
the tip (bale of cotton on a stick).
43. Epicoccum spp.
Microscopically: Hyphae typically form focal
repeated branching & rebranching
of certain threads forming masses
known as sporodochia.
Short conidiophore arise from these
masses.
Macroconidia are multi-celled,
muriform, spherical to slightly club
shaped.
Roughened on surface (blackish
wart like appearance).
45. Bipolaris spp.
Microscopically: Hyphae are dematiaceous & septate.
Conidiophores have knee like bends (geniculate)
Macroconidia are Elliptical to oval ,arranged
sympodially.
Thick walled, smooth surface.
Conidia when incubated in direct water or saline
mounts at 25 °C for 8 to 24 hours,
produce germ tube that arise from both the ends
of macroconidia (thus name bipolaris).
46. Drechslera spp.
Microscopically: Hyphae septate & darkly pigmented.
Geniculate conidiophore.
Cylindrical, multi-celled macroconidia
(sympodially).
In saline mounts single germ tube at right angle
to the long axis of conidium is formed.
47. Curvularia spp.
Microscopically: Hyphae are dematiaceous &
septate.
Conidiophore are geniculate &
twisted.
Conidia are golden brown,
arranged sympodially,
multi-celled.
Central cells grow more rapidly &
are larger than those at
ends(lighter) resulting in Curved
or “boomerang’’ appearance.
48. Exserohilum spp.
Microscopically: Hyphae are septate & dematiaceous.
Conidiophore are geniculate.
Conidia are produced sympodially.
Conidia are elongate, ellipsoid to
fusoid, pencil shaped & exhibit a
prominent hilum that is truncated &
protruding (arrows).
50. Nigrospora spp.
Macroscopically: Colonies are rapidly growing.
Cottony dirty white turn gray with maturity.
Reverse of colony also becomes pigmented.
Microscopically: Conidia are solitary, large subglobose,
smooth.
Jet black borne on tip of inflated urn shaped
conidiophore.
51. Phoma spp.
Macroscopically: Buff to dark brown.
Glabratous.
Microscopically: Large dark brown to black, smooth
walled, leathery, sac like called pycnidia.
Within Pycnidia are borne myriad cylindrical,
spindle shaped or spherical hyaline one celled
conidia.
52. Chaetomium spp.
Macroscopically: Initially white.
May become yellow, yellow-green.
or copper colored.
Microscopically: Large ,spiked hyphae simulating the legs of
spider.
53. Treatment Options
Medical Surgical
• Polyene.
• Flucytosine.
• Itraconazole.
• Voriconazole.
• Subcutaneous cyst.
• Ulcerative lesions- Debridement.
• Brain abscess- Debulking
Note: Eumycetomas in the extremities can be extremely difficult to manage, because of their
indolent nature, scarring, fistula formation, and bone involvement and the ability to obtain disease-
free tissue margins may be difficult via surgery, therefore adjunctive medical therapy is required.
54. Concluding Remarks
• Melanized fungi in general are underestimated as etiologic agents of varied clinical entities
primarily attributed to difficulties in classical identification owing to often slow growth and
poor morphology.
• However, this scenario has changed considerably with the introduction of molecular
diagnostics. Nearly all species can confidently be recognized by the rDNA ITS barcoding
marker.
• A majority of the melanized fungi are associated with non-life-threatening infections in the
clinical lab and are generally not reported.
• However, despite their rarity, they are highly relevant because of their potential to infect and
kill apparently healthy individuals.
55. • Chronic CNS infections may remain unnoticed for a long time, or are
misdiagnosed as tumors, and then take a fatal course.
• Disseminated and subcutaneous infections, such as chromoblastomycosis, are
recalcitrant to therapy and may relapse despite in vitro susceptibility to the
antifungals.
• The treatment options for melanized fungi are generally limited.
Yeasts are unicellular organisms that divide by budding. Most are non pathogenic but few are pathogenic, most important of them being Cryptococus neoformans.
Molds are multi cellular fungi that develop from spores which germinate to form vegetative hyphae.
Melanin dihydroxynaphthalene pigment.
Found mostly in soil.
Many of the organisms are mainly plant pathogens and humans act as accidental hosts.
Melanin dihydroxynaphthalene pigment.
Affecting only horny layer of epidermis.
Flat lesions.
Can tolerate upto 10% NaCl.
Hyper hydrotic- increased sweating more concentration of salt due to continuous evaporation therefore predilection to palms and soles (also increased density of sweat pores).
No or minimal inflammatory reaction.
Differentiated from D/D by: absence of scaling, induration, erythema, usually solitary.
Starts under the hair cuticle with formation of stony hard black nodules, which grow outside hair and completely envelope the shaft. Fungus can penetrate the cortex as well.
Nodules contain spores embedded in cement like substance or tightly packed mass of branched hyphae with numerous one celled asci containing ascospores.
Differentiate pediculosis by absence of pruritis and typical shape of eggs.
Differentiate from tinea capitis as hair shaft is normal on either side of cell mass in case of black Piedra and in case of tinea hair shaft as well as base and follicle is affected leading to alopecia, which is absent in black Piedra (but hair may break )
Granules contain tightly knit clusters of organisms within infected tissue
The infection is characterized by swelling, purplish discoloration, tumorlike deformities of the subcutaneous tissue, and multiple sinus tracts that drain pus containing yellow, white, red, or black granules. The colour of the granules is partly due to the type of infecting organism.
May affect any part of the body depending on the site of inoculation by trauma.
Secondary infection and ulceration may occur.
Sclerotic bodies, which are copper-colored, septate cells that appear to be dividing by binary fission and are thought by some to resemble copper pennies.
No propensity to disseminate.
PEH: pseudoepitheliomatous hyperplasia.
Epidermis plays an important role in Treansepidermal elimination (TEE) of fungus which may be visible as black dots on the surface of the lesion.
These black dots may be used as specimen for lab Dx of this infection.
The margins of these abscesses and granulomas are composed of giant cells, epithelioid cells, histiocytes, plasma cells, and lymphocytes.
Internal transcribed spacer
Universal barcode of fungi
