Mycoses and Dermatophytoses Overview

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Questions and Answers

Which organism is a common cause of Tinea corporis?

Microsporum

T.rubrum (correct)

T.mentagrophytes

E.floccosum

What is a key characteristic of Tinea cruris lesions?

They are typically located on the scalp.

They resemble flat plaques.

They exhibit serpiginous margins. (correct)

They are always pruritic.

Which of the following is a predisposing factor for Tinea cruris?

Frequent washing of the affected area

Low humidity conditions

Tight clothing (correct)

Exposure to sunlight

In Tinea unguium, infection primarily begins at which area of the nail plate?

The lateral or distal edges Signup and view all the answers

Which of the following genera is known for infecting hair and skin?

Microsporum Signup and view all the answers

What are common symptoms of Tinea manuum?

Peeling, dryness, and mild itching Signup and view all the answers

Tinea barbae is commonly known for which population?

Farm workers Signup and view all the answers

Which causative organism is responsible for Tinea pedis?

T.rubrum Signup and view all the answers

Which genus is primarily associated with infections of hair and skin only?

Microsporum Signup and view all the answers

What characteristic is associated with Microsporum canis?

Large, thick-walled, echinulate macroconidia Signup and view all the answers

Which of the following descriptions accurately represents Microsporum ferrugineum?

Causes tinea barbae and ectothrix infection Signup and view all the answers

What is a common infection caused by Epidermophyton floccosum?

Tinea pedis Signup and view all the answers

Which statement is true about Microsporum gypseum?

It has a cinnamon-colored colony with powdery appearance Signup and view all the answers

What is the primary causative organism for Endothrix tinea capitis?

Trichophyton violaceum Signup and view all the answers

Which of the following is NOT a type of tinea capitis presentation?

Tinea corporis Signup and view all the answers

What is a characteristic clinical symptom of Kerion?

Inflamed, painful nodules Signup and view all the answers

Ectothrix tinea capitis is primarily characterized by what type of hair damage?

Destruction of the hair cuticle Signup and view all the answers

Which organism primarily causes Favus or Tinea favosa?

Trichophyton schoenleinii Signup and view all the answers

A patient with scaling and small well-defined patches on the scalp most likely has which type of tinea capitis?

Ectothrix Signup and view all the answers

What is a distinct feature of Tinea pedis?

Athlete's foot symptoms Signup and view all the answers

Which symptom is associated with Favus?

Disc or cup-shaped yellow crusts Signup and view all the answers

Which type of dermatophyte primarily affects humans?

Anthropophilic Signup and view all the answers

What is the primary symptom of dermatophytosis?

Itching Signup and view all the answers

Which dermatophyte is identified as geophilic?

Microsporum gypseum Signup and view all the answers

Which of the following conditions can lead to dermatophytosis?

Crowded living conditions Signup and view all the answers

What is the term for a ringworm infection of the groin?

Tinea cruris Signup and view all the answers

Which of the following is a major source of ringworm infections?

Warm damp areas Signup and view all the answers

In the classification of dermatophytes, what does the term 'zoophilic' refer to?

Infections mainly found in animals Signup and view all the answers

Which form of dermatophytosis affects the scalp and hair?

Tinea capitis Signup and view all the answers

What does a negative result in the Hair Penetration Test indicate?

The infection is not present or limited to the outer skin layers. Signup and view all the answers

Which characteristic is specifically associated with Trichophyton tonsurans?

Causes endothrix infection with non-fluorescent hairs. Signup and view all the answers

What type of infection does Trichophyton verrucosum typically cause?

Ectothrix infection. Signup and view all the answers

What is a distinct feature of Trichophyton violaceum colonies?

Colony is deep violet with a purplish pigment diffusing into the media. Signup and view all the answers

Which type of conidia is produced by Trichophyton verrucosum?

Thin-walled macroconidia appearing as 'string beans'. Signup and view all the answers

What is a key microscopic feature of T. mentagrophytes

Teardrop microconidia. Signup and view all the answers

Which of the following statements is incorrect concerning the Hair Perforation Test?

All dermatophytes exhibit the same urease activity. Signup and view all the answers

How does T. schoenleinii primarily infect?

Demonstrates favic chandelier alignment in hair. Signup and view all the answers

What is the characteristic appearance of Trichophyton concentricum colonies?

Slow growing, wrinkled or folded, velvety Signup and view all the answers

Which of the following statements is true regarding Trichophyton mentagrophytes?

It can cause athlete's foot. Signup and view all the answers

What indicates a positive result in the Hair Penetration Test?

Fungal hyphae penetrating inside the hair shaft. Signup and view all the answers

Trichophyton rubrum is associated with which types of infections?

Tinea corporis and toenail infections Signup and view all the answers

Which characteristic distinguishes Trichophyton rubrum from Trichophyton mentagrophytes?

Type of hair penetration observed Signup and view all the answers

What is the primary method used for examining a hair sample in the Hair Penetration Test?

Using a KOH preparation for microscopic examination Signup and view all the answers

What color might Trichophyton concentricum colonies appear as?

White to orange to brown Signup and view all the answers

Which symbolic name is associated with the characteristic form of Trichophyton mentagrophytes?

Downy Signup and view all the answers

Study Notes

Mycoses Categories

Mycoses are categorized into cutaneous, subcutaneous, systemic, and opportunistic.
Cutaneous mycoses specifically affect the keratinized layers of skin, hair, or nails. Superficial cutaneous mycoses, specifically dermatophytoses, are included in this category.
Subcutaneous mycoses involve deeper skin layers.
Systemic mycoses affect multiple organ systems.
Opportunistic mycoses affect individuals with weakened immune systems.

Dermatophytoses

Dermatophytoses affect the keratinized layers of the skin, hair, or nails.
Symptoms include itching, scaling, ring-like skin patches, brittle and broken hair, and thick discoloured nails.
Dermatophytes are keratinophilic (keratin-loving).
Ringworm is a common name for dermatophytosis, named by the Greeks and Romans.

Dermatophytosis Classification

Dermatophytes are classified by their usual habitat: anthropophilic, geophilic, or zoophilic.
Anthropophilic dermatophytes infect humans.
Geophilic dermatophytes inhabit the soil and infect humans.
Zoophilic dermatophytes infect animals, but can also infect humans.

Dermatophytes Involved in Ringworm

Three anamorphic genera are involved in ringworm: Microsporum, Epidermophyton, and Trichophyton.
Microsporum species infect hair and skin only.
Epidermophyton species attack skin and nails only.
Trichophyton species attack skin, hair, or nails.

Pathogenesis and Immunity in Dermatophytosis

Contact and trauma can contribute.
Moisture plays a role in infection.
Crowded living conditions can increase risk.
Cellular immunodeficiency makes individuals more susceptible.
Chronic inflammation can worsen infection.
Re-infection is possible, but requires a larger inoculum.

Sites of Common Ringworm Infections

Schools
Military camps
Prisons
Warm damp areas
Animals

Modes of Transmission

Close human contact.
Sharing of items like clothes, combs, brushes, towels, and bedsheets (fomites).
Animal-to-human contact (zoophilic).

Types of Ringworm and Affected Sites

Tinea capitis affects the head, scalp, eyebrows, and eyelashes.
Tinea facialis affects the face.
Tinea corporis affects the body.
Tinea cruris affects the groin (jock itch).
Tinea unguium affects the nails.
Tinea barbae affects the beard.
Tinea manuum affects the hands.
Tinea pedis affects the feet (athlete's foot).
Tinea imbricata shows distinctive lesions.

Tinea capitis Clinical Presentations

Endothrix (black dot): Fungal elements invade hair without destroying the cuticle, often associated with a black dot appearance on the scalp.
Ectothrix (gray patch): Fungal elements destroy the hair cuticle; hyphae are then converted into infectious arthroconidia. Small well-defined patches are common.
Kerion: A complication of scalp ringworm caused by an overzealous immune response. The condition involves painful and inflamed nodules and plaques. Usually, of animal origin. Kerion heals, but potentially leaves some scarring.
Favus/Tinea favosa: This is the severe form of tinea capitis, characterized by the invasion of hair by hyphae. Common symptoms include yellow crusts (scutula) on the scalp, and a foetid odour.

Tinea corporis - Clinical Symptoms

Typically restricted to the stratum corneum of smooth skin.
Skin lesions form concentric or ring-like lesions.
Lesions may become inflamed.

Tinea cruris - Clinical Symptoms

Lesions tend to be circinate (ring-shaped) and serpiginous (snake-like)
Often found on the groin, inner thighs, and scrotum.
Factors like persistent perspiration, high humidity, tight clothing, and diabetes can exacerbate it.

Tinea cruris predisposing factors

Persistent perspiration
High humidity
Tight clothing
Diabetes
Obesity
Topical glucocorticoid application

Three Anamorphic Genera Involved in Ringworm

Microsporum: infects hair and skin only
Epidermophyton: attacks skin and nails only
Trichophyton: attacks skin, hair or nails.
Microsporum audouinii, M. canis, M. ferrugineum, and M. gypseum are included as Microsporum species.
Ringworm species include T. concentricum, T. mentagrophytes, T. rubrum, T. tonsurans, T. violaceum, T. verrucosum, and T. schoenleinii.

Tinea unguium- Clinical Symptoms

Infection typically begins at the edges of the nail plate.
Paronychia (inflammation around the nail) arises.
T. rubrum, T. mentagrophytes, and E. floccosum are common causative agents.

Tinea barbae- Clinical Symptoms

Commonly present in farm workers
Inflammatory lesions are common
T. mentagrophytes is the common causative organism.

Tinea manuum- Clinical Symptoms

Dermatophyte infection of the hands.
Zoophilic or geophilic fungus can cause it.
Anthropophilic fungus is usually the culprit.

Tinea pedis- Clinical Symptoms

Infection typically occurs between the toes or in toe webs.
It often releases clear fluid.
Common in the 4th and 5th toes.
Pruritic (itchy), scaly soles and painful fissures between toes are often found.
T. mentagrophytes, T. rubrum, and E. floccosum can be causative agents.

Hair Penetration Test- Procedure

Examining the scalp or affected area for fungal infections.
Cleaning the area to remove oils or debris.
Collecting hair strands using tweezers as close to the scalp as possible.
Microscopic examination of the hair sample using KOH (potassium hydroxide)
Observing for fungal hyphae or conidia inside the hair shaft.

Hair Penetration Test- Positive and Negative Results

Positive result: Fungal hyphae or conidia present inside hair shaft. This indicates fungal infection of the hair itself.
Negative result: No fungal elements seen inside the hair shaft. Infection is limited to the outer layers of the skin and does not involve the hair shaft.

Hair Penetration Test- Characteristics of Culture, Test and Microscopic Features

T. mentagrophytes: Positive in hair perforation test; microscopic features include tear-drop microconidia; culture positive in urea test.
T. rubrum: Negative in hair perforation test; microscopic features include clavate or peg-shaped microconidia; urea test negative.

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Description

This quiz explores the categories of mycoses, including cutaneous, subcutaneous, systemic, and opportunistic forms. It also delves into dermatophytoses, focusing on their symptoms, classification, and the characteristics of dermatophytes. Test your knowledge on fungal infections and their classifications.