Mycoses II Flashcards by ava mondschein

what is Superficial Mycoses and what are examples?

Cutaneous infections of keratinized tissues affecting the outermost layer of the skin, hair, and nail
- ring worm
- athletes foot
- jock itch
- pityriasis

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what is Subcutaneous Mycoses and what are some examples?

infection that occurs beneath the skin, often after trauma through cuts or wounds
- Sporotrichosis – from thorn pricks, known as “rose gardener’s disease”
- Mycetoma

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what is Systemic Mycoses and what are some examples?

inhaled dimorphic fungal spores cause infections of the internal organs
- Histoplasmosis
- Coccidioidomycosis
- Blastomycosis

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what is Opportunistic Mycoses and what are some examples?

fungi that are usually harmless in healthy individuals affect immunocompromised individuals
- Candidiasis (oral thrush, vaginal yeast infections)
- Cryptococcosis
- Aspergillosis
- Pneumocystis pneumonia (PCP)
- Mucormycosis

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what are the three main genera of Dermatophytes (Ascomycota) that cause Superficial Mycoses and what do they attack?

Trichophyton: skin hair nails
Microsporum: skin hair
Epidermophyton: skin nails

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What are Dermatophytes?

type of fungus that cause the most common skin infections worldwide and infect the skin, hair, and nails of humans and animals

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How do dermatophytes spread and cause symptoms?

close contact with infected soil, animals, or people but don’t spread easily or quickly and symptoms (like redness, itchiness, or rash) come from the body’s immune reaction to the fungi

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What is an “Id reaction”?

body reacts to the infection somewhere else on the skin by creating a sterile rash (no fungus there) called a dermatophytid, ide, or Id reaction

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how do Dermatophyte avoid the immune system?

fungus produces special proteins that help it stick to your cells and hide

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what is keratinase?

enzyme produced by fungi that breaks down keratin and proteinases

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What is Tinea?

fungal infection of the skin, hair, or nails where the name changes depending on the location

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what are the types of Tinea Infections?

Tinea corporis (Ringworm): Smooth, hairless (glabrous) skin
Tinea cruris (Jock Itch): Groin area
Tinea pedis (Athlete’s Foot): Feet, especially between toes
Tinea unguium (Onychomycosis): nails
Tinea capitis (Scalp Ringworm): scalp and hair shafts

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how does Tinea Corporis occur?

through minor skin trauma, fungi reside in hair follicles and invade the outer skin layer and growth spreads outward (centrifugally) forming a ring like lesion

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where does Tinea Corporis usually occur?

Can appear anywhere on the body but most frequently seen in moist areas

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what type of fungus is most frequently involved with Tinea Corporis?

Trichophyton rubrum

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What is Majocchi’s Granuloma?

rare but deeper fungal infection where tinea corporis penetrates into the dermis through hair follicles often happening due to trauma to the skin, such as shaving legs, scratching or abrasions.

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how does Tinea Pedis occur?

Maceration (softening from moisture) allows fungi to enter the skin and an environment with moisture, sweat, and poor ventilation (like in tight shoes) promote fungal growth

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where does Tinea Pedis usually occur?

Interdigital form: Occurs between the toes, especially 4th and 5th

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what type of fungus is most frequently involved with Tinea Pedis?

All three major dermatophyte genera can cause it:
- Trichophyton
- Epidermophyton
- Microsporum

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what causes Tinea Unguium (Onychomycosis)?

Trichophyton rubrum
Other possible fungi:
- Trichophyton tonsurans
- Epidermophyton floccosum
- Rarely: Microsporum gypseum

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what are risk factors for Tinea Unguium (Onychomycosis)?

Diabetes or poor blood circulation (peripheral vascular disease)
Wearing artificial nails (acrylics or wraps)
Aging (nail growth slows, and immune defenses weaken)

what is the appearance of Tinea Unguium (Onychomycosis)?

Nails become white or opaque, thickened, brittle and crumbly or distorted

how does Tinea Capitis (Ringworm of the Scalp) occur?

Fungi infect the scalp’s surface and invade hair follicles and the hyphae enter and damage the hair shaft, causing:
- Hair to break off at the scalp (leaving stubs or “black dots”)
- Blockage of follicles

what is the most common cause of Tinea Capitis (Ringworm of the Scalp)?

Trichophyton tonsurans
Other dermatophytes involved:
- Microsporum audouinii (non-inflammatory)
- M. canis, M. gypseum (inflammatory)

what are the anthropophilic fungi?

M. audouinii T. rubrum T. tonsurans T. mentagrophytes E. floccosum T. schoenleinii

what are the zoophilic fungi?

M. canis T. verrucosum T. mentagrophytes

what are the geophilic fungi?

M. gypseum

what are the main diagnostic methods of Dermatophyte (Fungal) Infections

- KOH Test (Potassium Hydroxide Prep) - Culture for Macro/Micro Morphology - Dermatophyte Test Medium (DTM)

what is Differential Diagnosis and what are examples?

Skin conditions that may look similar but aren't fungal - Erythrasma: bacterial infection - Contact Dermatitis: red, itchy rash - Pustular Psoriasis: inflammatory condition with scaly lesions and pustules - Nail Pitting: seen in psoriasis

how is the Trichophyton species identified?

By their microconidia (small spores). The shape varies: Round, Teardrop, Club-shaped, Pencil-shaped, etc. They may be numerous or rare, with thin or thick walls

how is the Microsporum species identified?

Mainly by macroconidia (sparse) These spores are: 🔹 Thick-walled, 🔹 Multicellular, 🔹 Shaped like spindles or blimps.

how is Epidermophyton floccosum identified?

Only produces macroconidia These spores are: 🔸 Thick-walled, 🔸 Cigar-shaped, 🔸 Smooth and multicellular.

how does Tinea Versicolor (aka Pityriasis Versicolor) occur?

caused by Malassezia furfur and Malassezia globosa (yeast-like fungi) that are lipophilic and found in hot, humid climates

what is the appearance of Tinea Versicolor (aka Pityriasis Versicolor)?

hypo-pigmented and hyper-pigmented scaly macules that form flaky patches that exfoliate from the surface or are continuous like they are growing together

where does Tinea Versicolor (aka Pityriasis Versicolor) occur?

Lesions can develop on many parts of the body - back, chest, shoulders, arms, neck, scalp, tongue, groin, legs

what does Tinea Versicolor (aka Pityriasis Versicolor) look like under a microscope?

spaghetti and meatballs

what is the fungus that causes Sporotrichosis?

Sporothrix schenckii

where is Sporothrix schenckii found and how are people infected?

found in soil, on plants and decaying organic matter and infect people exposed through work or hobbies involving outdoor or soil contact (farmers, gardeners, miners, etc)

does Sporothrix schenckii have zoonotic transmission?

yes, infected cats can transmit the disease to humans via scratches or bites

what does it mean that Sporothrix schenckii is a dimorphic fungus?

exists as mold in the environment at 25°C and transforms into cigar-shaped yeast in human tissue at 37°C

what are the initial infection manifestations of Sporotrichosis?

after a few weeks/months a painless papule (small bump) forms at the site and lymphatic channels nearby begin to thicken

what happens if Sporotrichosis lesions are left untreated?

they enlarge, become an open sore and develop into ulcers mainly along the lymphatic drainage route

how does Lymphocutaneous Sporotrichosis occur?

Infection starts under the skin and spreads through the lymphatic system to target organs like the eyes, bones, meninges (brain covering), and oral cavity

In Immunocompromised Patients (especially AIDS) what can occur?

Oral sporotrichosis can develop

what is Pulmonary Sporotrichosis (Rare)?

inhalation of fungal spores can cause lung infections considered an opportunistic infection, more likely in people with compromised immune systems

how is sporotrichosis (caused by Sporothrix schenckii) diagnosed?

through tissue samples by looking at - Yeast Cells stained with Periodic Acid-Schiff (PAS), which highlights fungal elements - amorphous eosinophilic (pink-stained) material, forming “asteroid bodies” or “rays” that surround yeast cells

what is Mycetoma?

A chronic subcutaneous infection caused by either: - Fungi → called Eumycetoma - Bacteria → called Actinomycetoma

what occurs with a Mycetoma infection?

granulomatous inflammation in the deep dermis and subcutaneous tissues that may extend to underlying bone and leads to swelling, tissue deformation, and chronic progression

what is Actinomycetoma (Bacterial Mycetoma) caused by?

Gram-positive, filamentous, anaerobic bacteria called Actinomyces israelii

what is the common name for an Actinomycetoma (Bacterial Mycetoma) infection and why?

lumpy jaw because it most commonly enters via decayed teeth and affects the face/jaw area

what are the clinical features/manifestations of Actinomycetoma?

a tumor-like mass due to chronic granulomatous inflammation that forms multiple sinus tracts that drain yellowish "sulfur granules" and leads to muscle spasms in the jaw