Pathology: Mycology

Mycology

It is the study of fungi.

Fungi

These are eukaryotic organisms that evolved in tandem with the animal kingdom.

Fungal cell

It has at least one nucleus with a nuclear membrane

Mycoses

It refers to infections that are caused by fungi.

Candidiasis and Dermatophytosis

These are mycoses with the highest incidence and are caused by fungi that are frequent components of the normal human microbiota and highly adapted to survival on the human host.

Arthroconidia

Conidia that result from the fragmentation of hyphal cells.

Blastoconidia

Conidia that are produced by budding.

Chlamydospores

Large, thick-walled, usually spherical conidia produced from terminal or intercalary hyphal cells.

Phialoconidia

Conidia that are produced by a “vase-shaped” conidiogenous cell.

Phialide

A “vase-shaped” conidiogenous cell that produces phialoconidia.

Dematiaceous Fungi

Fungi whose cell walls contain melanin, which imparts a brown to black pigment.

Dimorphic Fungi

Fungi that have two growth forms, such as a mold and a yeast, which develop under different growth conditions

Hyphae

Tubular, branching filaments (2–10 μm in width) of fungal cells, the mold form of growth.

Anamorph

The mitotic or asexual reproductive state of a fungus.

Mold

Hyphal or mycelial colony or form of growth.

Mycelium

Mass or mat of hyphae, mold colony.

Teleomorph

The sexual reproductive state of a fungus, which involves plasmogamy, karyogamy, and meiosis.

Pseudohyphae

Chains of elongated buds or blastoconidia; the septations between cells are constricted.

Septum

Hyphal cross-wall, typically perforated.

Sporangiospores

Asexual structures characteristic of the Order Mucorales.

Spore

A specialized propagule with enhanced survival value, such as resistance to adverse conditions or structural features that promote dispersion.

Sexual Spores

During sexual reproduction, haploid cells of compatible strains mate through a process of plasmogamy, karyogamy, and meiosis.

Ascospores

In the Phylum Ascomycota, following meiosis, four to eight meiospores form within an ascus.

Basidiospores

In the Phylum Basidiomycota, following meiosis, four meiospores usually form on the surface of a specialized structure, a club-shaped basidium.

Zygospores

In the Order Mucorales, following meiosis, a large, thick-walled zygospore develops.

Yeasts

Unicellular, spherical to ellipsoid (3–15 μm) fungal cells that usually reproduce by budding.

Mold

This form of growth occurs by the production of multicellular branching cylindrical tubules called hyphae that vary in diameter from 2 to 10 μm.

Yeasts

These are single cells, usually spherical to ellipsoid in shape and varying in diameter from 3 to 15 μm.

Carbohydrate layers

Glycoproteins

Lipids

It is what the cell wall of fungi composed of.

Malassezia Species

It is the causative agent of Pityriasis versicolor, a highly prevalent, chronic superficial infection of the stratum corneum.

Malassezia species

These lipophilic yeasts can be isolated from normal skin and scalp and are considered part of the cutaneous mycobiota.

Globosa, Furfur, and Sympodialis

Species of Malassezia that cause the vast majority of cases of pityriasis versicolor.

Pityriasis versicolor

This mycoses is characterized by discrete, serpentine, hyper-, or hypopigmented maculae that develop on the skin, usually on the chest, upper back, arms, or abdomen. These patches of discolored skin may enlarge and coalesce, but scaling, inflammation, and irritation are minimal.

Globosa, Furfur, Sympodialis, and Restricta

These species of Malassezia are the contributors to seborrheic dermatitis.

Tinea Nigra

It is a superficial chronic and asymptomatic infection of the stratum corneum caused by the dematiaceous fungus Hortaea (Exophiala) werneckii.

Hortaea (Exophiala) werneckii

It is the causative agent of Tinea Nigra, a condition that is more prevalent in warm coastal regions and among young women. The lesions appear as a dark (brown to black) discoloration, often on the palm.

Tinea Nigra

This infection causes skin scrapings from the periphery of the lesion revealing branched, septate hyphae and budding yeast cells with melanized cell walls.

keratolytic solutions, salicylic acid, or azole antifungal drugs

Treatment for Tinea Nigra.

Black Piedra

It is a nodular infection of the hair shaft.

Piedraia hortae

It is the causative agent of Black Piedra.

White Piedra

This infection presents as larger, softer, yellowish nodules on the hairs.

Trichosporon species

It is the causative agent of White Piedra.

Cutaneous mycoses

These mycoses are caused by fungi that infect only the keratinized tissue (skin, hair, and nails).

Microsporum, Trichophyton, and Epidermophyton

Three genera of dermatophytes.

Dermatophyte (ringworm)

In skin they are diagnosed by the presence of hyaline, septate, branching hyphae, or chains of arthroconidia.

Arthroderma

The several dermatophytic species that are capable of sexual reproduction produce ascospores and belong to the teleomorphic genus _____________.

Dermatophytes

These fungi are acquired by contact with contaminated soil or with infected animals or humans.

Anthropophilic species

These species of dermatophytes cause the greatest number of human infections. They elicit relatively mild and chronic infections, produce few conidia in culture, and may be difficult to eradicate.

geophilic, zoophilic, or anthropophilic

Classifications of dermatophytes depending on whether their usual habitat is soil, animals, or humans.

geophilic and zoophilic species

These species of dermatophytes being less adapted to human hosts, produce more acute inflammatory infections that tend to resolve more quickly.

anthropophilic species

Identify if the following are geophilic, zoophilic, or anthropophilic species of dermatophytes:

Epidermophyton floccosum, Trichophyton mentagrophytes var interdigitale, Trichophyton rubrum, and Trichophyton tonsurans

Microsporum gypseum

It is the most common geophilic species of dermatophytes causing human infections.

Microsporum canis

A zoophilic specie that causes dermatophytosis in dogs and cats.

Microsporum gallinae

A zoophilic specie that causes dermatophytosis in fowl.

Microsporum nanum

A zoophilic specie that causes dermatophytosis in pigs.

Trichophyton equinum

A zoophilic specie that causes dermatophytosis in horses.

Trichophyton verrucosum

A zoophilic specie that causes dermatophytosis in cattle.

T mentagrophytes

The colonial appearance of this Trichophyton specie may be cottony to granular; both types display abundant grape-like clusters of spherical microconidia on terminal branches. Coiled or spiral hyphae are commonly found in primary isolates.

T rubrum

The colonial appearance of this Trichophyton specie has a white, cottony surface and a deep red, non-diffusible pigment when viewed from the reverse side of the colony. The microconidia are small and piriform (pear-shaped).

T tonsurans

he colonial appearance of this Trichophyton specie produces a flat, powdery to velvety colony on the obverse surface that becomes reddish brown on reverse; the microconidia are mostly elongate.

M canis

A Microsporum specie that forms a colony with a white cottony surface and a deep yellow color on reverse; the thick-walled, 8- to 15-celled macroconidia frequently have curved or hooked tips.

M gypseum

A Microsporum specie that produces a tan, powdery colony and abundant thin-walled, four- to six-celled macroconidia.

Trichophyton species

A genera of dermatophytes that infects hair, skin, and nails.

Microsporum species

A genera of dermatophytes that infects hair and skin only.

E floccosum

A genera of dermatophytes that infects the skin and nails but not the hair.

E floccosum

The colonies of this pathogen are usually flat and velvety with a tan to olive-green tinge.

Anthropophilic species

These species of dermatophytes can be transmitted by direct contact or through fomites, such as contaminated towels, clothing, shared shower stalls, and similar examples.

Dermatophytes

These fungi are contagious and frequently transmitted by exposure to shed skin scales, nails, or hair containing hyphae or conidia. These fungal elements can remain viable for long periods on fomites.

Trichophytin

It is a crude antigen preparation that can be used to detect immediate- or delayed-type hypersensitivity to dermatophytic antigens.

Tinea pedis

It is the most prevalent of all dermatophytoses.

Tinea pedis (athlete’s foot)

This dermatophyte infection occurs in the interdigital spaces of the feet manifesting an itching, red vesicular in acute cases while scaling and fissures in chronic cases.

Tinea corporis (ringworm)

This dermatophyte infection occurs in non-hairy, smooth skin. Clinical features are circular patches with advancing red, vesiculated border, and central scaling.

Tinea cruris (jock itch)

This dermatophyte infection occurs in the groin. Clinical features are erythematous scaling lesion in intertriginous area.

Tinea capitis

This dermatophyte infection occurs in the scalp hair. Clinical features are Circular bald patches with short hair stubs or broken hair within hair follicles. Kerion rare. Microsporum-infected hairs fluoresce.

Tinea barbae

This dermatophyte infection occurs in the beard hair. Clinical features are edematous, erythematous lesion.

Tinea unguium (onychomycosis)

This dermatophyte infection occurs in the nail. Clinical features are thickened or crumbling nails distally; discolored; lusterless. Usually associated with tinea pedis.

Dermatophytid (id reaction)

This dermatophyte infection occurs usually sides and flexor aspects of fingers. Palm. Any site on body. Clinical features are Pruritic vesicular to bullous lesions. Most commonly associated with tinea pedis.

griseofulvin or terbinafine

Oral treatment for scalp infections (tinea capitis).

ketoconazole and itraconazole

Topical antifungal agent for scalp infections (tinea capitis)

itraconazole and terbinafine

Most effective drugs for tinea corporis, tinea pedis, and related infections.

2-4 weeks, 70-100%

Antifungal drugs for tinea corporis and tine pedis must be applied for at least __________________, the cure rates are usually ________________.

tinea unguium (nail infection)

This dermatophyte infection is the most difficult to treat, often requiring months of oral itraconazole or terbinafine as well as surgical removal.

traumatic inoculation

It is how the fungi that cause subcutaneous mycoses enter the skin of the host.

Sporothrix schenckii

It is a thermally dimorphic fungus that lives on vegetation.

Sporothrix schenckii

This fungus is associated with a variety of plants— grasses, trees, sphagnum moss, rose bushes, and other horticultural plants. At ambient temperatures, it grows as a mold, producing branching, septate hyphae and conidia, and in tissue or in vitro at 35–37°C as a small budding yeast.

Sporothrix schenckii

It is the causative agent of sporotrichosis, a chronic granulomatous infection.

sporotrichosis

The initial episode of this infection is typically followed by secondary spread with involvement of the draining lymphatics and lymph nodes.

S schenckii

This fungus grows well on routine agar media, and at room temperature the young colonies are blackish and shiny, becoming wrinkled and fuzzy with age.

S schenckii

This fungus is thermally dimorphic, and at 35°C on a rich medium it converts to growth as small, often multiply budding yeast cells that are variable in shape but often fusiform (about 1–3 × 3–10 μm).

Face

It is where the initial location of lesions for children with sporotrichosis.

primary pulmonary sporotrichosis

This infection results from inhalation of the conidia. This manifestation mimics chronic cavitary tuberculosis and tends to occur in patients with impaired cell-mediated immunity.

oral itraconazole

Treatment of choice for Sporotrichosis if the infection is self-limited.

amphotericin B

Treatment of choice for Sporotrichosis if the infection is systemic.

True

TRUE OR FALSE:

Males are more prone to Sporotrichosis due to increased exposure or because of an X-linked difference in susceptibility.

Sporotrichosis

It is considered as an occupational risk for forest rangers, horticulturists, and workers in similar occupations.

Chromoblastomycosis

It is a subcutaneous mycotic infection that is usually caused by traumatic inoculation of any of the recognized fungal agents, which reside in soil and vegetation.

Chromoblastomycosis

This infection is chronic and characterized by the slow development of progressive granulomatous lesions that in time induce hyperplasia of the epidermal tissue.

Phialophora verrucosa

A dematiaceous fungi wherein the conidia are produced from flask-shaped phialides with cup-shaped collarettes. Mature, spherical to oval conidia are extruded from the phialide and usually accumulate around it.

Fonsecaea pedrosoi

A dematiaceous fungi which form short branching chains of blastoconidia as well as sympodial conidia.

Fonsecaea compacta

A dematiaceous fungi which are almost spherical, with a broad base connecting the conidia. These structures are smaller and more compact than those of F pedrosoi.