MYCOLOGY (Intro-Subcutaneous Mycoses) Flashcards
a polysaccharide that is a vital component of the cell wall of fungi
CHITIN
fungi: eukaryotic or prokaryotic
EUKARYOTIC
respiration requirement of fungi
Obligate aerobes (require oxygen).
Single vegetative cells with smooth, creamy colonies (no aerial hyphae).
YEAST
yeasts divide thru:
Budding → Daughter cell (blastoconidium) forms, grows, and separates.
Fission → Two equal-sized cells form and divide after medial fission.
Fuzzy/woolly colonies due to mycelia (mass of hyphae).
MOLDS
Molds:
Fuzzy/woolly colonies due to ___ (mass of hyphae).
MYCELIA
mycelia that Extend above the colony, responsible for fuzzy appearance & conidia formation.
aerial mycelia
___ mycelia: Extend downward to absorb nutrients.
Vegetative mycelia:
___ hyphae → Moose antler-like tips.
___ hyphae → Club-shaped areas.
___ hyphae → Tightly coiled.
___ → Root-like structures (seen in Zygomycetes).
Antler hyphae → Moose antler-like tips.
Racquet hyphae → Club-shaped areas.
Spiral hyphae → Tightly coiled.
Rhizoids → Root-like structures (seen in Zygomycetes).
___ hyphae → Many cross-walls.
___ hyphae → Few irregular cross-walls.
Septate hyphae → Many cross-walls.
Sparsely septate hyphae → Few irregular cross-walls.
Moniliaceous
Hyaline
Dematiaceous
phaeoid
Light or non-pigmented.
hyaline
Dark due to melanin in the cell wall.
phaeoid
Stains for pigmentation:
_____ stain → Fungal elements appear black.
Gomori methenamine stain
Stains for pigmentation:
Gomori methenamine stain → Fungal elements appear _____.
black
_____ stain → Stains melanin (phaeoid = brown, hyaline = pink/red).
Fontana-Masson stain
Fontana-Masson stain → Stains melanin (phaeoid = _____, hyaline = _____).
(phaeoid = brown, hyaline = pink/red).
Can exist in two forms depending on temperature:
dimorphism
Yeast/spherule phase (___°C, high CO₂, in vivo).
Mold phase (___°C, ambient air).
Yeast/spherule phase (37°C, high CO₂, in vivo).
Mold phase (22–25°C, ambient air).
Thermally dimorphic fungi (human pathogens):
Blastomyces dermatitidis
Coccidioides immitis
Histoplasma capsulatum
Paracoccidioides brasiliensis
Sporothrix schenckii
Penicillium marneffei
Both yeast & mold forms present in the same culture (regardless of conditions), it is referred to as:
polymorphism
___ (Imperfect) Reproduction
Asexual (Imperfect) Reproduction
___ (Perfect) Reproduction
Sexual (Perfect) Reproduction
Formation of conidia (via mitosis). what reproduction
asexual
Conidiogenous cells (fruiting structures):
_____ → Produce phialoconidia (vase-like).
_____ → Produce annelloconidia (ringed).
_____ → Formed by fragmentation of hyphae.
Phialides → Produce phialoconidia (vase-like).
Annellides → Produce annelloconidia (ringed).
Arthroconidia → Formed by fragmentation of hyphae.
Conidiogenous cells (fruiting structures):
Phialides → Produce phialoconidia (___-like).
Annellides → Produce annelloconidia (___).
Arthroconidia → Formed by ___ of hyphae.
Phialides → Produce phialoconidia (vase-like).
Annellides → Produce annelloconidia (ringed).
Arthroconidia → Formed by fragmentation of hyphae.
Most mold identification is based on ____ structures.
Most mold identification is based on asexual structures.
Fusion of two nuclei + meiosis → Formation of _____ (sexual form).
telomorph
If a fungus has both sexual & asexual forms:
___ → Asexual form.
___ → Sexual form.
___ → Multiple anamorphs of the same teleomorph.
Anamorph → Asexual form.
Teleomorph → Sexual form.
Synanamorphs → Multiple anamorphs of the same teleomorph.
Single-celled, reproduce by budding/fission, creamy colonies.
Yeasts
Multicellular, hyphae (septate or sparsely septate), fuzzy colonies.
mold
___ = Dark (melanin),
___ = Light.
Phaeoid = Dark (melanin),
Hyaline = Light.
Asexual reproduction → ___ (important for lab ID).
conidia
Four major phyla associated with clinical infections:
Glomeromycota (Mucorales)
Ascomycota
Basidiomycota
Fungi Imperfecti (Deuteromycota)
Common genera: Lichtheimia (formerly Absidia), Mucor, Rhizomucor, Rhizopus.
WHAT PHYLUM
Mucorales (Phylum: Glomeromycota, formerly Zygomycota)
WHAT PHYLUM?
Fast-growing, opportunistic fungi, commonly found in soil.
Common genera: Lichtheimia (formerly Absidia), Mucor, Rhizomucor, Rhizopus.
Morphology:
Profuse gray to white aerial mycelium.
Hyaline, sparsely septate hyphae.
Reproduction:
Asexual reproduction → Sporangiospores inside a sporangium, supported by a sporangiophore.
Sexual reproduction (rare in clinical settings) → Zygospores.
Mucorales (Phylum: Glomeromycota, formerly Zygomycota)
WHAT PHYLUM?
Characterized by sexual spores = Ascospores (inside a sac-like structure called an ascus).
Most are identified by their asexual structures.
Clinically significant genera:
Dermatophytes: Microsporum spp., Trichophyton spp. (cause skin infections).
Pseudallescheria boydii: Causes mycetoma (chronic fungal infection of skin and soft tissue).
Ascomycota (Sac Fungi)
WHAT PHYLUM?
Few clinically significant pathogens.
Main human pathogen: Filobasidiella neoformans (the teleomorph or sexual form of Cryptococcus neoformans var. neoformans).
Identification challenges:
Basidiomycetous molds often remain sterile in the lab, making them difficult to identify.
Presence of clamp connections → Specialized hyphal structures that bypass septations.
Increasing recovery in labs, but clinical significance is unclear (may be environmental contaminants).
Basidiomycota (Club Fungi)
WHAT PHYLUM?
Largest group of medically important fungi (cutaneous, subcutaneous, systemic infections).
Lack a known sexual reproductive stage
Identified by their asexual reproductive structures.
Fungi Imperfecti (Deuteromycota)
___ PHYLUM→ Opportunistic molds, sporangiospores.
Mucorales (Glomeromycota)
___ PHYLUM → Ascospores in an ascus, mostly dermatophytes.
Ascomycota
___ PHYLUM → Clamp connections, Cryptococcus.
Basidiomycota
___ PHYLUM→ No sexual stage, major fungal pathogens.
Fungi Imperfecti
___ → Diseases caused by fungi.
Mycoses
MYCOSES Classified by site of infection:
___ Mycoses → Outer skin, hair.
___ Mycoses → Epidermis, nails, and deeper hair structures.
___ Mycoses → Deeper layers (muscle, bone, connective tissue).
___ Mycoses → Internal organs and deep tissues.
Superficial Mycoses → Outer skin, hair.
Cutaneous Mycoses → Epidermis, nails, and deeper hair structures.
Subcutaneous Mycoses → Deeper layers (muscle, bone, connective tissue).
Systemic Mycoses → Internal organs and deep tissues.
___ Mycoses
📍 Affect only the outermost skin layer or hair; no inflammation.
📍 Often cosmetic rather than serious.
Superficial
___ Mycoses (Dermatophytoses)
📍 Infect keratinized tissues (epidermis, nails, hair).
📍 Cause inflammation and pruritus.
🔹 Dermatophytes (Major Genera):
Trichophyton → Hair, skin, nails.
Microsporum → Hair, skin.
Epidermophyton → Skin, nails.
🔹 Common Infections (Tinea or “Ringworm”)
Cutaneous
Dermatophytes (Major Genera):
___ → Hair, skin, nails.
___ → Hair, skin.
___ → Skin, nails.
Trichophyton → Hair, skin, nails.
Microsporum → Hair, skin.
Epidermophyton → Skin, nails.
___ → Hair loss.
___ → Classic ringworm.
___→ “Jock itch”.
___→ “Athlete’s foot”.
___→ Thick, brittle nails.
Capitis (Head) → Hair loss.
Corporis (Body) → Classic ringworm.
Cruris (Groin) → “Jock itch”.
Pedis (Feet) → “Athlete’s foot”.
Unguium (Nails) → Thick, brittle nails.
___ → “Copper pennies” in tissue.
Chromoblastomycosis
___ → Granules in drainage.
Eumycotic mycetoma
___ → Follows lymphatic spread, no granules.
Sporotrichosis
___ → Chronic “wart-like” nodules.
Chromoblastomycosis
___ → Gardening, lymphatic spread.
Sporotrichosis
___ → Deep tissue destruction, granules in pus.
Mycetoma
___ Mycoses (Disseminated Fungal Infections)
Systemic
What Opportunistic Systemic Mycosis?
pulmonary disease
ABPA (allergic bronchopulmonary aspergillosis)
Aspergillosis
What Opportunistic Systemic Mycosis?
Oral Thrush
Esophagitis
Systemic infections
Candidiasis
What Opportunistic Systemic Mycosis?
Meningitis in AIDS patients
Cryptococcosis
What Opportunistic Systemic Mycosis?
rhinocerebral infection
angioinvasion
Mucormycosis
_____ = Hides in macrophages (Ohio/Mississippi).
Histoplasma
____ = Broad-based budding yeast.
Blastomyces
___ = Southwest deserts (Valley Fever).
Coccidioides
___ = CNS infections, capsule (India ink test).
Cryptococcus
___ = Septate hyphae, 45° branching.
Aspergillus
___ mycoses are fungal infections limited to the cornified (stratum corneum) layers of the epidermis. These infections generally do not cause inflammation or tissue response, making them asymptomatic in most cases. Patients often seek treatment for cosmetic concerns rather than medical necessity.
Superficial
what fungi?
Clinical Manifestations
Causative agent of tinea versicolor, a condition characterized by patchy lesions or scaling of varying pigmentation.
Also associated with dandruff.
Malassezia furfur
what fungi?
Hypopigmented in dark-skinned individuals.
Fawn-colored or “liver spots” in light-skinned individuals.
More noticeable during warm months due to sun exposure.
Malassezia furfur
KOH preparation: Shows budding yeasts (4-8 µm) with septate hyphae (“spaghetti and meatballs” appearance).
Malassezia furfur
Malassezia furfur Wood’s lamp: ___ fluorescence.
Yellow
Causative agent of black piedra, a fungal infection of the hair shaft.
Piedraia hortae
Forms hard, dark brown to black gritty nodules firmly attached to scalp hair.
Nodules contain asci (sac-like structures) with eight ascospores.
Endemic in tropical areas of Africa, Asia, and Latin America.
WHAT FUNGI?
Piedraia hortae
KOH preparation of infected hairs: Nodules can be crushed to reveal asci.
Microscopy: Thick-walled rhomboid cells containing ascospores.
Piedraia hortae
Culture: Grows slowly on Sabouraud dextrose agar at room temperature, forming brown, restricted colonies that remain sterile.
Piedraia hortae
Common Sites: Face, chest, trunk, abdomen.
Not typically treated with antifungals but can be managed with antidandruff shampoos.
Can cause disseminated infections in infants receiving lipid replacement therapy (managed by removing feeding lines).
Malassezia furfur
Pathogenesis & Risk Factors
Normal skin colonizer, requires lipids for growth.
Factors influencing overgrowth:
Corticosteroid therapy (↓ squamous epithelial cell turnover).
Genetic factors.
Poor nourishment & excessive sweating.
Geographic prevalence: Hot, humid, tropical locations.
Malassezia furfur
Culture requirements: Does not grow on routine fungal media without lipid supplementation (e.g., olive oil overlay). Colonies appear cream-colored, moist, and smooth.
Malassezia furfur
Causative agent of white piedra, characterized by soft, white mycelial nodules on scalp, face, and pubic hair.
Trichosporon spp.
Most clinically significant Trichosporon spp., can cause severe, often fatal systemic disease in immunocompromised patients.
T. asahaii
Trichosporon spp. that can cause meningitis (often isolated from CSF).
T. mucoides
____ piedra is endemic in tropical regions of South America, Africa, and Asia.
White
Primary fungal media: Rapid growth.
Trichosporon spp.
Positive for urease.
No carbohydrate fermentation.
Uses potassium nitrate & assimilates sugars.
Trichosporon spp.
Colony appearance:
Straw to cream-colored, yeastlike.
Varies between smooth, wrinkled, dry, or moist textures.
Trichosporon spp.
Causative agent of tinea nigra.
Hortaea werneckii
Causes brown to black nonscaly macules, often found on:
Palms of hands
Soles of feet
Hortaea werneckii
No inflammatory or tissue reaction.
Potential for misdiagnosis as malignant melanoma, leading to unnecessary surgical procedures.
Hortaea werneckii
Endemic in tropical regions of Central & South America, Africa, and Asia.
Hortaea werneckii
Culture characteristics:
Produces shiny, moist, yeastlike colonies.
Initially brown, later turning olive to greenish-black.
Hortaea werneckii
rapid growth, urease positive
Trichosporon spp (White piedra
KOH prep - asci with ascospores
Black piedra (Piedraia hortae)
___→ Lipid-dependent, causes tinea versicolor (spaghetti & meatballs appearance).
Malassezia furfur
___ → Hard black nodules on hair (black piedra).
Piedraia hortae
___→ Soft white nodules on hair (white piedra), systemic disease in immunocompromised patients.
Trichosporon spp.
___ → Brown/black macules on palms/soles (tinea nigra), may mimic melanoma.
Hortaea werneckii
___ Mycoses
Keratinophilic Nature: These fungi thrive on keratin-rich structures like hair, nails, and skin.
Cutaneous
___ Mycoses
Infection & Pathology:
Rarely invade deep tissues but can cause inflammation and nail bed involvement.
Some species exhibit teleomorphic (sexual) stages but are mostly studied in their anamorphic (asexual) state.
Cutaneous
___ (what infection)
Causative Agent: Trichophyton schoenleinii.
Tinea favosa (Favus)
___ (what infection)
Symptoms: Crusty lesions (scutula), hair loss, and scar formation.
Tinea favosa (Favus)
___ (Scalp Ringworm)
Tinea capitis
___ infection): Microsporum audouinii, Microsporum ferrugineum.
Gray Patch Ringworm (ectothrix infection)
___infection): Trichophyton tonsurans, Trichophyton violaceum.
Black Dot Ringworm (endothrix infection):
Symptoms:
Nails become thick, discolored, and flaky.
Strong correlation with tinea pedis (athlete’s foot).
Onychomycosis
Treatment Challenges:
Long-term therapy with terbinafine or itraconazole.
Often unsatisfactory treatment results.
Infections Involving the ___
Nails (Onychomycosis)
___
Transmission: Infected skin scales from carpets, showers, or floors.
Tinea Pedis (Athlete’s Foot)
Symptoms:
Scaling, fissuring, and erythema of the soles and toe webs.
Tinea Pedis (Athlete’s Foot)
Severe cases lead to a “moccasin foot” appearance.
Tinea Pedis (Athlete’s Foot)
___: Concentric ring lesions on the trunk.
Tinea imbricata (Trichophyton concentricum)
Produces macroconidia (smooth, thin-walled, beaver-tail shaped).
Epidermophyton floccosum
Colony: Yellow to tan, feathered edges.
Found worldwide.
Epidermophyton floccosum
___:
Macroconidia: Spindle-shaped, echinulate, thick-walled.
Microsporum canis:
___:
Colony: Fluffy white, lemon-yellow underside.
Worldwide distribution.
Microsporum canis:
___:
Macroconidia: Fusiform, moderately thick-walled, up to six cells.
Microsporum gypseum:
___:
Colony: Powdery, granular with tan-to-buff conidial masses.
Geophilic, found in soil worldwide.
Microsporum gypseum:
___:
Slow-growing anthropophilic species.
Colony: Cottony white with little or no reverse pigmentation.
Once a major cause of tinea capitis in children.
Microsporum audouinii:
___:
Microconidia: Globose to tear-shaped, in grape-like clusters.
Trichophyton mentagrophytes:
Macroconidia: Cigar-shaped, smooth-walled.
Trichophyton mentagrophytes:
Colony: Granular or downy, varies with conidia production.
Rapid-growing, found worldwide.
Trichophyton mentagrophytes:
Macroconidia: Cylindric, three to eight cells.
Trichophyton rubrum:
Microconidia: Clavate- or peg-shaped.
Trichophyton rubrum:
Colony: White surface, red to burgundy pigment on reverse.
Global distribution.
Trichophyton rubrum:
Microconidia: Variable shape (round to peg-like).
Trichophyton tonsurans:
Colony: Rust-colored pigment on Sabouraud dextrose agar.
Trichophyton tonsurans:
Leading cause of tinea capitis in children worldwide.
Trichophyton tonsurans:
Other names: Verrucous dermatitidis, Chromomycosis
- Chromoblastomycosis
Epidemiology & Etiology
Occurs worldwide, but is most common in tropical/subtropical regions (Americas, Africa, Texas, Louisiana)
Caused by:
Fonsecaea compacta
Fonsecaea pedrosoi
Phialophora verrucosa
Cladophialophora carrionii
Rhinocladiella aquaspersa
Chromoblastomycosis
Clinical Manifestations:
- Chronic, slow-growing skin infection
- Develops over months to years, often asymptomatic unless secondary complications arise
Affects extremities (feet, lower legs) due to trauma
Chromoblastomycosis
Verrucous nodules that may ulcerate and crust
Chromoblastomycosis
Lesions:
Cauliflower-like surface in advanced cases
Chromoblastomycosis
Lesions:
Presence of sclerotic bodies (brown, round, non-budding structures) is diagnostic
Chromoblastomycosis
Laboratory Diagnosis
Microscopy: Sclerotic bodies in tissue
Chromoblastomycosis
Culture Characteristics:
Darkly pigmented (phaeoid) molds
Moderate to slow growth
Velvety to woolly colonies (gray-brown to olivaceous black)
Chromoblastomycosis
Endemic in India, Africa, South America
Eumycotic Mycetomas
Causative Fungi:
Pseudallescheria boydii (most common in the U.S.)
Acremonium falciforme
Madurella mycetomatis
Madurella grisea
Exophiala spp.
Eumycotic Mycetomas
Clinical Manifestations
Subcutaneous swelling with sinus tract formation
Eumycotic Mycetomas
Clinical Manifestations
Draining purulent or serous fluid containing fungal granules
Can lead to bone involvement and deformities if untreated
Eumycotic Mycetomas
Direct Microscopy: Differentiates between eumycotic and actinomycotic mycetomas
Eumycotic Mycetomas
Culture Characteristics:
P. boydii: White-to-dark gray colonies, grows rapidly at 22°C and 35°C
A. falciforme: Grayish-brown/violet, slow-growing
Madurella spp.: Slow-growing, produces brown pigment
Eumycotic Mycetomas
Microscopy Findings:
P. boydii: Oval conidia borne singly on annellides
A. falciforme: Slightly curved conidia held in mucoid clusters
Madurella spp.: Sterile hyphae, phialides producing conidia (in ~50% of M. mycetomatis)
Eumycotic Mycetomas
Common agents:
Exophiala dermatitidis
Exophiala spp.
Other Hyphomycetes, Coelomycetes, and Ascomycetes
Subcutaneous Phaeohyphomycosis
Clinical Manifestations
Chronic nodular or cystic lesions at trauma site
May spread locally but rarely disseminates
Subcutaneous Phaeohyphomycosis
Laboratory Diagnosis
Microscopy: Septate, branched hyphae; yeast-like cells (solitary or short chains)
Culture:
Exophiala spp.: Olivaceous to black colonies
E. dermatitidis: Initially yeast-like, then velvety at maturity
Conidia borne from annellides (except E. dermatitidis, which uses phialides)
Subcutaneous Phaeohyphomycosis
Caused by: Sporothrix schenckii
Sporotrichosis
High-risk activities:
Gardening (Rose Handler’s Disease)
Exposure to sphagnum moss
Sporotrichosis
Direct Microscopy:
Cigar-shaped yeast in tissues (seen in Gram stains, but often scarce)
Sporotrichosis
Culture:
Dimorphic growth: Mold form at 22°C, yeast form at 37°C
Initial colonies: White, glabrous, yeast-like → Darker, mycelial over time
Conversion to yeast on brain heart infusion agar at 37°C (CO2 incubator needed)
Sporotrichosis
Microscopy from Culture:
Thin, delicate hyphae with rosette pattern conidia at conidiophore tips
Dark-walled conidia along hyphae
Sporotrichosis
cigar-shaped yeast, rosette candida
Sporotrichosis
Key lab feature:
Pigmented hyphae
Subcutaneous phaeohyphomycosis
