Basic and clinical Mycology

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Questions and Answers

What is the main reason fungi cannot synthesize their own food?

They are prokaryotic.

They live in anaerobic conditions.

They do not have cell walls.

They lack chlorophyll pigment. (correct)

Which of the following correctly describes the structure of fungal cell walls?

They are purely made of cellulose.

They are absent in fungi.

They are made primarily of chitin. (correct)

They contain peptidoglycan.

What is a defining feature of coenocytic hyphae?

They are divided into distinct cell-like units.

They contain no septum. (correct)

They contain cross walls.

They are primarily used for sexual reproduction.

Which type of fungi is characterized as non-filamentous and unicellular?

Yeasts Signup and view all the answers

What type of fungal reproduction involves the fragmentation of the mycelium?

Vegetative reproduction Signup and view all the answers

Which of the following statements is true regarding the cytoplasm of fungi?

It contains mitochondria and endoplasmic reticulum. Signup and view all the answers

In the classification of fungi, molds are defined by:

Their growth as long filaments forming a mat. Signup and view all the answers

What is a major difference between fungi and bacteria?

Fungi possess a eukaryotic nucleus. Signup and view all the answers

Which of the following substances is not found in the cell membrane of fungi?

Cholesterol Signup and view all the answers

What process enables yeasts to grow in the absence of oxygen?

Facultative anaerobic growth Signup and view all the answers

What process involves the splitting of a parent yeast cell into two equal halves?

Fission Signup and view all the answers

Which type of fungal spores are motile and produced inside zoosporangia?

Zoospores Signup and view all the answers

What type of reproduction involves only the somatic portion of the fungal thallus?

Vegetative reproduction Signup and view all the answers

Which term describes a compact mass formed by interwoven hyphae that can remain dormant?

Sclerotia Signup and view all the answers

In which type of fusion do motile gametes of the same size undergo fusion?

Isogamy Signup and view all the answers

What is NOT a characteristic of dermatophytes?

They invade underlying tissues. Signup and view all the answers

Which spore type is formed by the breaking up of hyphal cells and does not store reserve food?

Oidia Signup and view all the answers

What is the primary method of laboratory diagnosis for fungal infections?

Direct microscopic examination Signup and view all the answers

What type of fungal infection is tinea versicolor caused by?

Malassezia furfur Signup and view all the answers

Which of the following statements about sexual reproduction in fungi is false?

Occurs in fungi imperfecti. Signup and view all the answers

What is the disease caused by Cladosporium werneckii?

tinea nigra Signup and view all the answers

Which treatment is recommended for chromomycosis?

Flucytosine or thiabendazole plus local surgery Signup and view all the answers

What common characteristic is shared by Coccidioides immitis, Histoplasma capsulatum, and Blastomyces dermatitidis?

Thermally dimorphic Signup and view all the answers

What is the primary mode of transmission for Cryptococcus neoformans?

Inhalation of fungal spores Signup and view all the answers

Which condition is primarily associated with Aspergillus fumigatus?

Aspergillosis Signup and view all the answers

Which clinical finding is typical of sporothricosis?

Local abscess with nodules in lymphatics Signup and view all the answers

What is a characteristic feature of mucormycosis?

Not dimorphic Signup and view all the answers

What symptoms are associated with paracoccidioidomycosis?

Asymptomatic in most cases Signup and view all the answers

Which treatment is used for Candida albicans infections, like oral thrush?

Miconazole or nystatin Signup and view all the answers

What is a common clinical finding in cases of coccidioidomycosis?

Influenza-like illness with fever and cough Signup and view all the answers

Study Notes

Basic Mycology

Fungi are heterotrophic, meaning they get their nutrition from other organisms, unlike plants that can produce their own food.
Fungi can be either parasites, obtaining nutrients from living hosts, or saprophytes, feeding off of dead or decaying organic matter.
The fungal body, called the mycelium, consists of filaments called hyphae.
The cell wall of fungi is composed of chitin and other polysaccharides.
Fungi are typically aerobic or facultative anaerobes, meaning they can thrive in the presence or absence of oxygen.
Some fungi exhibit thermal dimorphism, meaning they can exist in two forms: yeast and mold.
Fungi are distinct from bacteria in several ways:
- They have a larger diameter.
- They have a eukaryotic nucleus, unlike bacteria's prokaryotic nucleus.
- They have a cell membrane containing ergosterol and zymosterol, which bacteria lack.
- Fungi have a different cell wall composition compared to bacteria.
- Fungi are generally not sensitive to antibiotics.

Types of Fungi

Molds are filamentous fungi that form a mat called a mycelium.
- Thallus is the body of the mold, consisting of interconnected hyphae.
- Hyphae are individual filaments.
- Septate hyphae have cross walls called septa, dividing them into distinct cells.
- Coenocytic hyphae lack septa and appear as single continuous cells with multiple nuclei.
Yeast are non-filamentous, single-celled fungi that are spherical or oval.
- They are often found as a white powder on fruits and leaves.
- Yeast can grow anaerobically, unlike most fungi.

Fungal Reproduction

Vegetative Reproduction: Involves the somatic portion of the fungus.
- Fragmentation: The mycelium breaks into pieces, each capable of growing into a new mycelium.
- Budding: The parent cell produces a bud that detaches and grows into a new individual. Common in yeast.
- Fission: The parent cell splits into two equal halves, each forming a new individual. Also common in yeast.
- Sclerotia: Hyphae compact together and form a hard, dormant structure that can survive unfavorable conditions.
- Rhizomorphs: Interwoven hyphae form rope-like structures that can grow into new mycelia.
Asexual Reproduction: Involves the formation of spores resulting from mitosis.
- Zoospores: Flagellated, motile spores produced inside structures called zoosporangia. They lack a cell wall.
- Sporangiospores: Non-motile spores produced inside sporangia.
- Chlamydospores: Thick-walled resting spores that store food.
- Oidia: Spore-like structures formed by the breaking up of hyphae.
- Conidia: Non-motile spores produced singly or in chains at the tip of hyphae.
Sexual Reproduction: Involves the fusion of gametes, gametangia, or hyphae.
- Planogametic Copulation: Fusion of motile gametes.
  - Isogamy: Fusion of two morphologically similar gametes.
  - Anisogamy: Fusion of two motile gametes that differ in size.
  - Heterogamy: Fusion of a smaller, motile male gamete with a larger, non-motile female gamete.
- Gametangial Contact: Gametangia come close and form a fertilization tube for the male gamete to migrate into the female gametangium.
- Gametangial Copulation: Gametangia fuse and develop into a zygospore.
- Spermatization: Tiny unicellular spores called spermatia are transferred to female gametangia for fertilization.

Fungal Pathogenesis

The body's response to fungal infections often involves granuloma formation.
Fungal transmission can occur through airborne, cutaneous, or percutaneous routes.
Infections can result from colonization, reactivation of latent infections, or direct transmission.

Laboratory Diagnosis of Fungal Infections

Direct microscopic examination of samples.
Culture of the fungus.
Serological tests to detect antibodies against fungal antigens.

Fungal Infections

Cutaneous Mycoses (Superficial Fungal Infections):
- Dermatophytes:
  - Tinea: Infections caused by dermatophytes, including:
    - Tinea capitis: Scalp infection.
    - Tinea cruris: Groin infection.
    - Tinea pedis: Foot infection.
    - Tinea unguium: Nail infection.
  - Transmission: Direct contact with humans or animals, infected hairs or skin scales.
  - Pathogenesis: Grow in the superficial layers of the skin and do not invade deeper tissues.
  - Treatment: Topical antifungals (miconazole, clotrimazole, tolnaftate) or oral griseofulvin.
  - Prevention: Keep skin dry and cool.
- Malassezia furfur:
  - Tinea versicolor: Skin infection characterized by hypopigmented areas, scaling, and itching.
  - Transmission: Skin scales.
  - Treatment: Topical miconazole.
- Cladosporium werneckii:
  - Tinea nigra: Skin infection characterized by black or brown macules on the palms.
  - Transmission: Skin injury.
  - Treatment: Salicylic acid.
Subcutaneous Mycoses:
- Sporothrix schenckii:
  - Sporotrichosis: Infection characterized by local abscesses or ulcers, and nodules along lymphatic vessels.
  - Transmission: Traumatic penetration of skin.
  - Treatment: Potassium iodide or ketoconazole.
  - Prevention: Protect skin while gardening.
- Phialophora and Cladosporium species:
  - Chromomycosis: Infection characterized by wart-like lesions and crusting abscesses.
  - Transmission: Trauma to skin.
  - Treatment: Flucytosine or thiabendazole with local surgery.
Systemic Mycoses:
- Coccidioides immitis:
  - Coccidioidomycosis: Infection characterized by influenza-like symptoms, fever, and cough.
  - Transmission: Inhalation of fungal spores.
  - Treatment: Amphotericin B or ketoconazole.
- Histoplasma capsulatum:
  - Histoplasmosis: Infection characterized by asymptomatic infection, primarily involving the respiratory tract. Dissemination can lead to granulomas in various organs.
  - Transmission: Inhalation of fungal spores.
  - Treatment: Amphotericin B or ketoconazole.
- Blastomyces dermatitidis:
  - Blastomycosis: Infection often asymptomatic, mostly affecting the respiratory tract. Dissemination can lead to ulcerative granulomas in the skin, bones, and other areas.
  - Transmission: Inhalation of fungal spores.
  - Treatment: Ketoconazole.
- Paracoccidioides brasiliensis:
  - Paracoccidioidomycosis: Infection with various clinical presentations, including asymptomatic infection, mucosal lesions, pulmonary lesions, skin lesions, and other organ involvement.
  - Transmission: Inhalation of fungal spores.
  - Treatment: Ketoconazole.
Opportunistic Mycoses:
- Candida albicans:
  - Candidiasis: Infection often occurring in the mouth (thrush) or vagina (vaginitis).
  - Transmission: Not person-to-person.
  - Clinical Findings: Whitish plaques on mucous membranes.
  - Treatment: Nystatin or miconazole.
- Aspergillus fumigatus:
  - Aspergillosis: Infection characterized by invasion of blood vessels, thrombosis, infarction, and formation of aspergilloma (fungal ball).
  - Transmission: Inhalation of fungal spores.
  - Treatment: Amphotericin B or steroid therapy.
- Cryptococcus neoformans:
  - Cryptococcal Meningitis: Infection characterized by influenza-like symptoms, pneumonia, and eventual spread to the brain (meningitis).
  - Transmission: Inhalation of fungal spores.
  - Treatment: Amphotericin B and flucytosine.
- Mucor and Rhizopus:
  - Mucormycosis: Infection affecting individuals with diabetes or leukemia. Primarily involves the nose and sinuses, leading to mucosal invasion, necrosis, and infarction.
  - Transmission: Inhalation of fungal spores.
  - Treatment: Amphotericin B and surgical debridement.

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Test your knowledge on the fascinating world of fungi! This quiz covers various aspects of mycology, including nutritional modes, structure, and classification of fungi. Challenge yourself and learn more about their unique characteristics and importance in the ecosystem.