MYCOLOGY
FUNGI
• Classified as thallophytes
• Possess true nuclei
• Heterotrophic members of plant family that lack
stems and roots
• Do not possess chlorophyll
• Larger and more complex than the bacteria
Unicellular YEAST PHASE
- creamy, resembling bacterial colony
Multicellular MOLD PHASE
- cottony, mycelial mass
YEAST
• Unicellular fungi
• MICROSCOPIC
• Oval to round
• Budding
• Bud = blastospore
• Pseudohyphae
MONOMORPHIC YEAST
•Candida albicans
•Cryptococcus neoformans
•Geotrichum candidum
MOLD
• Multicellular
• Hypha (2-10 um)
• MYCELIA
• Vegetative/ thallus
• Reproductive/ aerial
MOLD
• MACROSCOPIC
• Cottony, wooly, velvety,
granular, filamentous, hairy
• MONOMORPHIC MOLD
• Microsporum
• Epidermophyton floccosum
• Trichophyton
DIMORPHIC FUNGI
• Mold (infective to man): Room Temp (25OC)
• Yeast(aka tissue/in vivo/invasive phase) : 37OC
MONOMORPHIC FUNGI
• One growth phase only (e.g Sepedonium – mold at 25 and 37 degrees C)
DIPHASIC FUNGI
• mold at 25 and 37 degrees C
• Yeast – tissues
DIMORPHIC FUNGI
• Sporothrix schenckii
• Histoplasma capsulatum
• Blastomyces dermatitidis
• Coccidioides immitis
• Paracoccidiodes brasiliensis
• Penicillium marneffei
SUBCELLULAR STRUCTURE OF
FUNGI
• CAPSULE
• STRUCTURE: Polysaccharide
• FUNCTION: Antiphagocytic factor
• CELL WALL
• Antigenic
• Multilayered
• Polysaccharides, proteins, glycoproteins
• Functions:
• Provides shape, rigidity & strength
• Protection from osmotic shock
• Mediates attachment to host cells
MAJOR POLYSACCHARIDES OF
FUNGI CELL WALL
POLYMER
Chitin
Chitosan
Cellulose
Alpha-Glucan
Beta-Glucan
Mannan
MONOMER
N-acetyl glucosamine
D-glucosamine
D-glucose
D-glucose
D-glucose
D-mannose
SPORES INVOLVED IN SEXUAL
REPRODUCTION
Ascospores
Zygospores
Oospores
Basidiospores
Contained in a saclike ascus (6-8
ascospores)
Involve the fusion of two identical
cells arising from the same hypha
Involve the fusion of cells from two
separate, non-identical hyphae
Contained in a club-shaped
basidium
FUNGI THAT EXHIBIT A SEXUAL PHASE ARE KNOWN AS THE
PERFECT FUNGI
SPORES INVOLVED IN ASEXUAL
REPRODUCTION
Conidia
Spores produced singly or multiply
in long chains or clusters by
specialized vegetative hyphae
known as conidiophores
a. Macroconidia – large,
multicellular
b. Microconidia – small,
unicellular
Blastoconidia (blastospores)
Develops as daughter cell buds off
the mother cell and is pinched off
SPORES INVOLVED IN ASEXUAL
REPRODUCTION
Chlamydoconidia
(chlamydospores)
Thick walled, resistant, resting
spores produced by rounding up,
and enlargement of terminal
hyphal cells
The spores germinate when
favorable environmental conditions
occur
a. Terminal – end of hypha
b. Intercalary - within hyphal
strand
c. Sessile – side of hypha
Arthroconidia
Involve the simple fragmentation of
the mycelium; useful identification
feature of C.immitis and
G.candidum
SPORES INVOLVED IN ASEXUAL
REPRODUCTION
Sporangiospores
Spores contained in a sporangia or
sacs that are produced terminally
on sporangiophore or aseptate
hyphae; unique to zygomycetes
LABORATORY DIAGNOSIS OF
FUNGAL INFECTIONS
•Direct Microscopic Examination
•Culture
•Serology & Biochemical Tests
MICROSCOPIC METHOD
Saline mount
10% KOH mount
Demonstration of fungal hyphae
Dissolves/ destroys keratin layer
Sample: keratinized tissue (skin, hair, nails)
-OH
• Clears debris
• Makes fungi prominent
Lactophenol Cotton Blue (Aman’s medium)
Fungal cell wall: blue
• Lactic acid: help preserve fungi
• Phenol: kill any live org.
• Cotton blue
India Ink/ Nigrosin
Capsule: Unstained
Background: Black
“capsules (clear halo) against dark background”
- Capsule of C. neoformans
MICROSCOPIC METHOD
Calcofluor white stain (fluorescence microscopy)
For dermatophytes
Not suitable for Pneumocystis carinii
Binds w/ chitin in cell wall
Under Wood’s light/UV light
Apple-green/ bluish white fluorescence
TESTS
• Germ Tube Test
•
•
•
•
• Hair Baiting Test
Candida albicans
• V shaped penetration of hair shaft
0.5 mL rabbit serum + a colony
T. mentagrophytes (+)
Incubate for 2 ½ -3 hrs @ 37 degrees C T. rubrum (-)
(+) Germ tube formation
• Exoantigen test
• L-DOPA ferric citrate test
• Serologic confirmation for systemic fungi
• Test for phenoloxidase
• Microscopic immunodiffusion test w/
antisera
• (+) black – C. neoformans
Demonstration of
• Urease test
specific A bands: B. dermatitidis
• (+) control: C. neoformans
H & M bands: H. capsulatum
• (-) control: C. albicans
SUPERFICIAL MYCOSES
MALASSEZIA FURFUR
• Naturally found on the skin surfaces of many animals, including humans.
• Isolated in 18% of infants and 90-100% of adults
• May be spread from person to person, fomites
Tinea/ Pityriasis Versicolor
• usually characterized by hypopigmented or
hyperpigmented macules and patches on the
chest and the back
• Inpatients with a predisposition, tinea versicolor
may chronically recur
• fungal infection is localized to the stratum
corneum
• High temperature,humidity favour occurrence
• Degradation of lipids leads to production of acids
and eventual destruction of melanocytes
TINEA NIGRA
• Hortaea werneckii
• dematacious fungus
• dark (brown to black)
discoloration
• Lab diagnosis: skin
scrapings w/ branched
septate hyphae &
budding yeast cells
BLACK PIEDRA
• Piedraia hortai
• nodular infection of the
shaft
• black nodules like
pebbles
WHITE PIEDRA
• Trichosporon beigelli
• larger, softer yellowish
nodules on the Hairs, axilla,
pubic, beard,
• scalp
CUTANEOUS MYCOSES
(DERMATOMYCOSES)
• Trichophyton
• Infection of skin, hair, and nails
• Microsporum
• Infection of skin and hair
• Not the cause of tinea unguium
• Epidermophyton
• Infection of skin and nails
• Not the cause of tinea capitis
M. canis (zoophilic)
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•
•
•
M. gypseum
(geophilic)
• 3-9 celled, broadly spindle-shaped, rough-walled macroconidia
• Terminal ends rounded
• Microconidia, if present, single or in small clusters
M.audouinii
(anthrophilic)
• Conidia absent or bizarre if present
• Atypical vegetative hyphae with terminal chlamydospores
• APPLE-GREEN FLUORESCENCE OF ECTOTHRIX HAIRS
E. floccosum
• Large, multicelled, club-shaped, smooth-walled macroconidia,
single or in clusters of 2-3
• MICROCONIDIA NOT FORMED
T. rubrum
• Macroconidia are few, smooth-walled, pencil-shaped, attached
directly to hyphae
• Microconidia are tear-shaped single and lateral along hyphae
• Abundant wine-red, water-soluble pigment
• (-) hair baiting, (-)urease
Large, multicelled, spindle-shaped, rough macroconidia
Terminal ends sometimes curved
Microconidia few or absent
GREEN-YELLOW FLUORESCENCE OF ECTOTHRIX HAIRS
T. mentagrophytes
• Macroconidia are few, smooth-walled, cigar-shaped, connected
to hyphae with definite narrow attachment
• Microconidia are spherical, often in grape-like clusters spiral
hyphae
• Scant red pigment in some strains
• (+)hair baiting, (+) urease
T. tonsurans
• Macroconidia absent or rare, distorted
• Many microconidia of various size and shapes with flattened
base
• “balloon forms” –aged pleomorphic microconidia
T. verrucosum
• Macroconidia rare, 3-5 cells, thin-walled, “rat-tail”
• Microconidia are large, clavate, lateral
T. schoenleinii
• Conidia absent
• Favic chandeliers and chlamydospores common
T. violaceum
• Conidia absent
• Swollen hyphae containing cytoplasmic granules
CANDIDA ALBICANS
• oval yeast with a single bud or as
pseudohyphae
• part of normal commensal of the body;
can become opportunistic
• predisposing factors:
immunocompromised state
• Diseases caused:
• Oral thrush, Vulvovaginitis, Skin infections,
Diaper rash, Intertrigo, onychomycosis
SUBCUTANEOUS MYCOSES
SPOROTHRIX SCHENKII
• KOH exam of aspirates, pus, biopsy
materials (typically unrewarding)
• Tissue smears (often negative,
sensitivity enhanced by GMS, PAS,
FAB)
• Round-oval, cigar-shaped yeast cells
• Asteroid bodies (H&E) in tissue: central
halo around degenerating yeast;
concentric radiating eosinophilic
material (Ag-Ab rxn)
SPOROTHRIX SCHENKII
DIMORPHIC FUNGUS
• RT:
• Mold- flowerette conidia
(conidia in cluster)
• In older cx – conidia on
side of hyphae (sleeve)
• 37OC – yeast: cigar-shaped
yeast cells
SPOROTHRIX SCHENKII
• fine, septate hyphae and rosette/daisy-like clusters of
conidia on thin conidiophores
SPOROTHRIX SCHENKII
• SPOROTRICHOSIS/ Rose
gardener’s disease
CHROMOBLASTOMYCOSIS
• Dematiaceous fungi (dark, slow-growing
fungi)
• Microscopic exam: SCLEROTIC BODIES
a) Fonsecaea – mixed sporulation
Arotheca – conidia in side
Cladosporium – conidia in chain
Phialophora – conidia in cluster
b) Phialophora – only phialophora
sporulation
c) Cladosporium – only Cladosporium
sporulation
MYCETOMA
• Granulomatous disease of subcutaneous tissue
1. Eumycotic (true fungi)
Exophiala
Pseudoallescheria boydii MC cause of mycetoma
2. Actinomycotic (fungus-like bacteria) → do not stain
with fungal stain
Actinomyces – w/ sulfur granules
Nocardia
PHAEOHYPHOMYCOSIS
• Rare infection caused by dematiaceous saprobes w/c
invade organs (skin, lungs, brain) of
immunosuppressed hosts
Exophiala (former Phialophora) jeanselmei
Phialophora
Wangiella (former Fonsecaea) dermatitidis
Cladosporium trichoides
SYSTEMIC MYCOSES
BLASTOMYCOSIS
• North American
Blastomycosis
• pulmonary infection (via
inhalation of conidia)
• Blastomyces dermatitidis
COCCIDIODOMYCOSIS
• Coccidioides immitis
• pulmonary infection (inhalation of
Arthrospores)
• dark skinned Type B males
• Influenza-like illness
• Lung infiltrates, adenopathy, or effusions
• Erythema nodosum (desert bumps)
• Arthralgias (desert rheumatism)
• Meningitis
HISTOPLASMOSIS
• Histoplasma capsulatum
• ”great mimic”
• affects RES of macrophages in
lungs
• Respiratory via inhalation of
airborne microconidia
PARACOCCIDIOIDOMYCOSIS
• Paracoccidiodes brasiliensis
• South American Blastomycosis
• ulcerative granulomata of the buccal,
basal, skin, adrenals, GIT
• Thick yeast of with multiple buds in
wheel configuration “captain’s /
mariner’s wheel” formation
SYSTEMIC MYCOSES
ORGANISM
North American Blastomycosis
Gilchrist’s Disease
Blastomyces dermatitidis
South American Blastomycosis
Paracoccidioides brasiliensis
Darling’s disease
Histoplasma capsulatum
San Joaquin Valley Fever/ Valley
Fever/ Desert Fever
Coccidioides immitis
MYCELIAL PHASE (RT)
YEAST PHASE (37OC/ TISSUES)
Delicate, septate hyphae with round
or pyriform conidia borne singly on
conidiophores or directly on hyphae,
resembling “lollipops”
Thick-walled, large yeast cells with
single bud on a broad base: broad
isthmus at constriction
Small, septate, branched hyphae with
intercalary and terminal
chlamydoconidia; few piriform
microconidia
Large, round to oval, thick walled
yeast cells with multiple buds, which
attach to mother cell by narrow
constrictions; resembles a ship wheel
Septate hyphae with round to piriform
microconidia on short branches or
directly on hyphal stalk; later, large,
round, thick-walled knobby
tuberculated macroconidia forms
Small, budding, round to oval yeast
cells; intracellular to mononuclear
cells possible with Giemsa or Wright’s
stain
Coarse, septate, branched hyphae that
produce thick-walled barrel-shaped,
rectangular arthroconidia that
alternate with empty disjunctor cells
Large, round, thick-walled spherules
with endospores observed in tissue
and direct examination; not a true
yeast
OPPORTUNISTIC
CANDIDA ALBICANS
• oval yeast with a single bud or as
pseudohyphae
• part of normal commensal of the body;
can become opportunistic
• predisposing factors:
immunocompromised state
• Diseases caused:
• Oral thrush, Vulvovaginitis, Skin infections,
Diaper rash, Intertrigo, onychomycosis
CRYPTOCOCCOSIS
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•
•
•
Cryptococcus neoformans
skin lesions, CNS lesions
immunocompromised host
Grows abundantly in soil containing bird (especially
pigeon) droppings
• Diagnosis:
• India ink (clear halo) and mucicarmine (red inner
capsule),
• Cryptococcal Antigen Latex Agglutination System
(CALAS) of the CSF
• Fungal culture
Cryptococcus neoformans
• Encapsulated yeast cell in bird and bat droppings
• Demonstration of the capsule by india ink stain
• Urease positive, inositol positive, nitrate negative
• Cultured on
• SDA medium w/o cycloheximide
• Birdseed/nigerseed/Staib’s (assimilates creatinine)
• Latex agglutination test for cryptococcal Ag in CSF
ASPERGILLOSIS
• Aspergillius fumigatus, Aspergillius flavus, Aspergillius
niger
• Transmission: Respiratory via inhalation of airborne
conidia
• Septate hyphae that form V-shaped (dichotomous)
branches
• Aspergillus may cause a broad spectrum of disease in
the human host, ranging from hypersensitivity
reactions to direct angioinvasion
• ALLERGIC BRONCHOPULMONARY ASPERGILLOSIS
• IgE-mediated
• Asthma-type reaction with shortness of breath, high fever, and
expectoration of brownish bronchial plugs
• ASPERGILLOMA
• Fungus ball
• associated with hemoptysis
• Monod sign: air around aspergilloma
• INVASIVE ASPERGILLOSIS
• necrotizing pneumonia
• may disseminate to other organs in immune-compromised patients
• (+) air crescent sign on radiography
PNEUMOCYSTIS JIROVECI/CARINII
• PNEUMOCYSTIS JIROVECII PNEUMONIA
• Occurs when CD4 <200
• Most common AIDS-defining illness
• Cysts in the alveoli induce an
inflammatory response
• consisting plasma cells - frothy exudate
that blocks oxygen exchange
• 100% mortality if untreated