Introduction to Fungi and Their Classification
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Questions and Answers

Pityriasis versicolor is caused by the fungus Malassezia furfur.

True

Tinea infections are exclusively caused by viruses.

False

Candidiasis is a type of superficial mycosis.

True

Tinea capitis refers to a fungal infection of the foot.

<p>False</p> Signup and view all the answers

Skin scrapings with KOH microscopy are used for diagnosing fungal infections.

<p>True</p> Signup and view all the answers

Fungi are prokaryotes and are susceptible to antibiotics.

<p>False</p> Signup and view all the answers

Yeasts reproduce by budding and are unicellular.

<p>True</p> Signup and view all the answers

Dimorphic fungi can grow as both yeast and mould depending on environmental conditions.

<p>True</p> Signup and view all the answers

Hyphae are the reproducing bodies of moulds.

<p>False</p> Signup and view all the answers

Chitin is a component of the fungal cell wall that provides rigidity.

<p>True</p> Signup and view all the answers

Candida albicans is a yeast-like fungus that only grows in its yeast form.

<p>False</p> Signup and view all the answers

Fungal infections are not recognized as important in clinical settings.

<p>False</p> Signup and view all the answers

Moulds consist of unicellular organisms with waxy colonies.

<p>False</p> Signup and view all the answers

Sporotrichosis is commonly known as 'Rose Pickers Disease'.

<p>True</p> Signup and view all the answers

Histoplasma capsulatum grows as yeasts at 25oC and as moulds at 37oC.

<p>False</p> Signup and view all the answers

Sporothrix schenckii can enter the body through a break in the skin.

<p>True</p> Signup and view all the answers

Histoplasma capsulatum is commonly found in Ireland and the UK.

<p>False</p> Signup and view all the answers

Diagnosis of sporotrichosis can include tissue biopsy.

<p>True</p> Signup and view all the answers

Candida is a normal flora found in the mouth, intestine, and lower genital tract.

<p>True</p> Signup and view all the answers

Aspergillus is primarily a unicellular organism.

<p>False</p> Signup and view all the answers

Topical antifungal agents like Clotrimazole are used to treat Candida infections.

<p>True</p> Signup and view all the answers

Aspergillus can cause allergic reactions in sensitive individuals.

<p>True</p> Signup and view all the answers

Candida infections do not occur in immunosuppressed individuals.

<p>False</p> Signup and view all the answers

Allergic broncho pulmonary aspergillosis is a hypersensitivity reaction associated with asthma and cystic fibrosis.

<p>True</p> Signup and view all the answers

Invasive aspergillosis primarily affects healthy individuals without any known risk factors.

<p>False</p> Signup and view all the answers

Surgery is always required for treating aspergilloma.

<p>False</p> Signup and view all the answers

A common diagnostic technique for fungal infections is serology.

<p>True</p> Signup and view all the answers

Fluid filled cavities on CXR/CT Thorax are not associated with aspergilloma.

<p>False</p> Signup and view all the answers

Eosinophilia and high IgE levels are indicative of invasive aspergillosis.

<p>False</p> Signup and view all the answers

Neutropenia is a significant risk factor for invasive fungal disease.

<p>True</p> Signup and view all the answers

The use of broad spectrum antibiotics can increase the risk of invasive fungal infection.

<p>True</p> Signup and view all the answers

Sporothrix schenckii is a type of fungus involved in cutaneous mycoses.

<p>True</p> Signup and view all the answers

Histoplasma capsulatum is commonly found in Ireland and the UK.

<p>False</p> Signup and view all the answers

Disseminated infections from sporotrichosis can affect the liver, lungs, and central nervous system.

<p>True</p> Signup and view all the answers

Eosinophilia is a common sign of sporotrichosis.

<p>False</p> Signup and view all the answers

Microscopy has low sensitivity for the diagnosis of Histoplasma capsulatum infections.

<p>True</p> Signup and view all the answers

Pityriasis versicolor commonly causes white patches on the skin.

<p>False</p> Signup and view all the answers

Dermatophyte fungi can be acquired from animals, humans, and soil.

<p>True</p> Signup and view all the answers

Tinea pedis refers to a fungal infection of the groin.

<p>False</p> Signup and view all the answers

Skin scrapings are often used to diagnose superficial mycoses.

<p>True</p> Signup and view all the answers

Tinea capitis is associated with fungal infections of the face.

<p>False</p> Signup and view all the answers

Yeast reproduce by fission and are multicellular.

<p>False</p> Signup and view all the answers

Moulds consist of clumps of intertwined branching hyphae.

<p>True</p> Signup and view all the answers

Dimorphic fungi can exist in a unicellular form but not as moulds.

<p>False</p> Signup and view all the answers

Chitin is a component of the fungal cell wall that enhances its rigidity.

<p>True</p> Signup and view all the answers

Cryptococcus is an example of a multicellular fungus.

<p>False</p> Signup and view all the answers

Fungi are susceptible to antibiotics.

<p>False</p> Signup and view all the answers

Candida albicans grows exclusively in its yeast form.

<p>False</p> Signup and view all the answers

Fungal infections are often considered clinically significant due to their potential severity.

<p>True</p> Signup and view all the answers

Aspergillus is primarily a filamentous fungus found in decomposing organic matter.

<p>True</p> Signup and view all the answers

Erythema lesions caused by Candida infections are usually found in dry areas of the skin.

<p>False</p> Signup and view all the answers

Fluconazole is solely used as a topical treatment for Candida infections.

<p>False</p> Signup and view all the answers

Aspergilloma is a type of invasive infection caused by Aspergillus.

<p>False</p> Signup and view all the answers

Clinical diagnosis of Candida infections might include skin scrapings and swabs.

<p>True</p> Signup and view all the answers

Aspergillus can lead to both allergic reactions and invasive diseases.

<p>True</p> Signup and view all the answers

Fluid filled cavities in the lungs are always indicative of invasive aspergillosis.

<p>False</p> Signup and view all the answers

Eosinophilia and high IgE levels suggest allergic broncho pulmonary aspergillosis.

<p>True</p> Signup and view all the answers

Allergic broncho pulmonary aspergillosis can be effectively treated with antifungals alone.

<p>False</p> Signup and view all the answers

Central venous catheters are considered a risk factor for invasive fungal infections.

<p>True</p> Signup and view all the answers

Invasive aspergillosis primarily spreads through the bloodstream to organs like the liver and spleen.

<p>True</p> Signup and view all the answers

Sputum positivity for Aspergillus indicates a higher chance of invasive infection.

<p>False</p> Signup and view all the answers

Only individuals with healthy immune systems can develop invasive aspergillosis.

<p>False</p> Signup and view all the answers

Pityriasis versicolor can cause pale brown or pink macules on the trunk and neck.

<p>True</p> Signup and view all the answers

Tinea pedis is a fungal infection that primarily affects the nails.

<p>False</p> Signup and view all the answers

Candida infections are solely limited to the superficial skin layers.

<p>False</p> Signup and view all the answers

Dermatophyte infections can be acquired through contact with contaminated soil.

<p>True</p> Signup and view all the answers

Malassezia furfur is responsible for causing tinea capitis.

<p>False</p> Signup and view all the answers

Hyphae are the unicellular reproductive bodies of moulds.

<p>False</p> Signup and view all the answers

All fungi are obligate pathogens and require a host to survive.

<p>False</p> Signup and view all the answers

Chitin is the main component of the fungal cell wall that provides rigidity.

<p>True</p> Signup and view all the answers

Dimorphic fungi can exist as moulds in high temperatures and as yeasts in lower temperatures.

<p>False</p> Signup and view all the answers

Candida albicans is a yeast-like fungus known to reproduce solely by fragmentation.

<p>False</p> Signup and view all the answers

Moist, mucoid colonies characterize yeast such as Cryptococcus.

<p>True</p> Signup and view all the answers

Invasive fungal disease is less likely to affect individuals who are neutropenic.

<p>False</p> Signup and view all the answers

Fungi are classified as prokaryotes and are susceptible to typical antibacterial treatments.

<p>False</p> Signup and view all the answers

Sporotrichosis can disseminate to the central nervous system.

<p>True</p> Signup and view all the answers

Histoplasma capsulatum is primarily endemic in European countries.

<p>False</p> Signup and view all the answers

The diagnosis of sporotrichosis can include sputum culture.

<p>True</p> Signup and view all the answers

Histoplasma capsulatum reproduces exclusively in its yeast form.

<p>False</p> Signup and view all the answers

Pulmonary sporotrichosis is contracted primarily through inhalation of fungal spores.

<p>False</p> Signup and view all the answers

Candida can only cause superficial infections and does not lead to systemic infections.

<p>False</p> Signup and view all the answers

Aspergillus primarily thrives in hospital environments and is commonly found in soil, air, and decomposing matter.

<p>True</p> Signup and view all the answers

The primary treatment for invasive Candida infections is topical antifungal agents.

<p>False</p> Signup and view all the answers

Allergic Bronchopulmonary Aspergillosis (ABPA) is characterized by a reaction to Aspergillus antigens in sensitized individuals.

<p>True</p> Signup and view all the answers

Discrete white patches on mucosal surfaces are a common symptom of Candida mucosal infections.

<p>True</p> Signup and view all the answers

Fluid filled cavities on CXR/CT Thorax are a common indicator of invasive aspergillosis.

<p>False</p> Signup and view all the answers

High IgE levels and eosinophilia are indicative of allergic broncho pulmonary aspergillosis.

<p>True</p> Signup and view all the answers

Invasive aspergillosis can only affect individuals with a known pre-existing condition.

<p>False</p> Signup and view all the answers

Aspergillus infections can spread to various organs including the liver and central nervous system.

<p>True</p> Signup and view all the answers

Antifungal treatments are effective for treating aspergilloma.

<p>False</p> Signup and view all the answers

Prolonged ICU admission is a risk factor for invasive fungal infection.

<p>True</p> Signup and view all the answers

Coughing up blood is a common symptom of invading aspergillosis.

<p>False</p> Signup and view all the answers

Microscopy and culture are essential diagnostic techniques used for fungal infections.

<p>True</p> Signup and view all the answers

Study Notes

Introduction

  • Fungi are eukaryotes
  • Can be non-pathogenic, primary pathogens, or opportunistic pathogens
  • Fungi are not susceptible to antibiotics

Fungal Structure

  • Cell Membrane: phospholipid bilayer, surrounds cytoplasm, contains Ergosterol
  • Cell Wall: Chitin + carbohydrates (ß-d-glucan and mannans), chitin cell wall gives rigidity, antigenic
  • Capsule: present in some fungi, polysaccharide, antiphagocytic virulence factor

Classification of Fungi

  • Yeast: Unicellular (spheroid or ellipsoid), reproduce by budding, Moist, mucoid, or waxy colonies
  • Yeast-like Fungi: Grow partly as yeast and partly as elongated cells resembling hyphae (pseudohyphae), reproduce by budding, Generally creamy white colonies
  • Mould or Filamentous Fungi: Multicellular, made up of clumps of intertwined branching hyphae, grow by longitudinal extension, Produce spores
  • Dimorphic Fungi: Can grow either as a yeast or mould depending on environmental conditions and temperature

Definitions

  • Hyphae: Tubules made up of fungal cells attached end to end, growth = extend in length from tip of tubules
  • Spores: The reproducing bodies of moulds

Examples of Fungi

  • Cryptococcus: Yeast
  • Candida albicans: Yeast-like fungi
  • Dermatophyte Fungi: 3 genera: Trichophyton spp, Epidermophyton spp, Microsporum spp

Types of Fungal Infections

  • Superficial: Limited to outermost layers of skin, hair, nails and mucosa
  • Invasive:
    • Subcutaneous: involves deeper layers of dermis and subcutaneous tissue
    • Systemic: Spread to internal organs

Superficial Mycoses

  • Pityriasis versicolor: Malassezia furfur, patchy rash, pale brown/pink macules, Itchy, Trunk/Neck most common
  • Dermatophytosis (Ringworm/tinea): Caused by dermatophyte fungi, acquired from humans/animals/soil
  • Candidiasis: (Discussed in latter half of lecture)

Diagnosis of Superficial Mycoses

  • Clinical diagnosis
  • Skin scrapings (KOH - microscopy)

Pityriasis Versicolor

  • Diagnosis: Clinical appearance, Wood’s Light, Skin scrapings

Tinea

  • Diagnosis: Clinical appearance, Skin scrapings/nail clippings, Microscopy (treat first with KOH to clear keratin), Culture on selective media (Sabouraud agar)
  • Clinical Manifestations: Tinea barbae (beard), Tinea capitis (head), Tinea corporis (body), Tinea cruris (groin), Tinea faciei (face), Tinea manuum (hand), Tinea pedis (foot), Tinea unguium (nail)

Subcutaneous Mycoses

  • Sporotrichosis: Sporothrix schenckii (dimorphic fungus), Initial ulcer develops into granulomatous nodule
  • Clinical Spectrum: Cutaneous/Lymphocutaneous, Pulmonary, Disseminated

Diagnosis of Sporotrichosis

  • Microscopy (KOH)
  • Culture (Sabouraud agar): Tissue biopsy, Sputum, Body fluid
  • Histopathology

Dimorphic Fungal Infection: Histoplasma capsulatum

  • Grow as moulds at 25oC, yeasts at 37oC
  • Found in soil, guano from birds & bats, Caves!

Clinical Presentation

  • Asymptomatic infection
  • Acute/chronic respiratory infection resembling TB
  • Disseminated, involving liver, lungs, spleen (immunosuppressed patients)
  • Fungus lives intracellular in macrophages => immune-evasion

Diagnosis of Histoplasma capsulatum

  • Antigen detection: Urine and/or serum
  • Culture: Tissue, blood, body fluid (Can take up to 6 weeks)
  • Histopathology
  • Microscopy: Low sensitivity
  • Serology

Candida

  • Normal flora: mouth, intestine and lower genital tract
  • Opportunist pathogens, (increasing importance)
  • Superficial (skin + mucosal) & systemic infections

Candida Skin Infections

  • Erythema, plaque-like lesions, satellite lesions, warm, moist areas
  • Precipitants: Antibiotics, steroids, pregnancy, immunosuppression

Diagnosis & Treatment of Candida Skin Infections

  • Diagnosis: Clinical appearance, Skin scrapings, swabs
  • Treatment: Topical antifungal agents (Clotrimazole), Oral antifungal (Fluconazole)

Candida Mucosal Infections

  • Discrete white patches on mucosal surface: Oral, vaginal, oesophageal
  • Diagnosis: Swab for microscopy & culture
  • Treatment: Topical (Clotrimazole), Oral antifungal (fluconazole)

Candida Invasive Infections

  • Candida blood stream infection
  • Infective endocarditis
  • Peritonitis
  • Osteomyelitis
  • Arthritis
  • Endophthalmitis

Aspergillus

  • Mould/filamentous fungus
  • Found in soil, air, plants and decomposing organic matter

Aspergillus Pathogenesis

  • Allergy due to reaction to Aspergillus antigens in atopic individuals (ABPA)
  • Spore-forming organism: spores inhaled, germinate to form hyphae

Clinical Manifestations:

  • Allergic aspergillosis: Sinusitis, Allergic Bronchopulmonary Aspegillosis (ABPA)
  • Aspergilloma
  • Invasive aspergillosis (more in: Introduction to opportunistic infection lecture)

Allergic Bronchopulmonary Aspergillosis (ABPA)

  • Hypersensitivity reaction, asthma, cystic fibrosis
  • Bronchospasm, obstruction, wheeze, cough, SOB, fever
  • Eosinophilia, high IgE
  • Diagnosis: High antibody titres in serum, fleeting CXR changes
  • Treatment: Steroids +/- itraconazole

Aspergilloma

  • Damaged lung (TB, CF, COPD)
  • Asymptomatic, chronic cough, haemoptysis
  • Diagnosis: Sputum positive in 66%, antibodies positive in 70%, fluid-filled cavity on CXR/CT Thorax
  • Treatment: Surgery in some cases, No role for antifungals

Invasive Aspergillosis

  • Risk groups – Neutropenia, transplant, HIV
  • Spread from primary site to other sites (liver, spleen, kidney, CNS)
  • Invasion of blood vessels

Diagnostic techniques used to identify Fungi

  • Clinical diagnosis
  • Microscopy and Culture
  • Antigen detection
  • Serology
  • Histopathology
  • Radiology

Risk Factors for Invasive Fungal Infection

  • Haematological malignancy
  • Haematopoietic stem – cell transplant
  • Solid Organ transplant
  • Neutropenia
  • Extremes of age
  • Abdominal surgery
  • Prolonged ICU admission
  • Central venous catheter
  • Use of broad spectrum antibiotics
  • Renal failure

Fungi

  • Eukaryotic organisms found worldwide
  • Can be non-pathogenic, primary pathogens, or opportunistic pathogens
  • Not susceptible to antibiotics

Fungal Structure

  • Cell membrane: Consists of a phospholipid bilayer surrounding the cytoplasm and containing ergosterol
  • Cell wall: Composed of chitin, β-d-glucan, and mannans. Chitin provides rigidity and is antigenic.
  • Capsule: Present in some fungi, composed of polysaccharides, and acts as an antiphagocytic virulence factor

Classification of Fungi

  • Yeast: Unicellular, reproducing by budding. Colonies are moist, mucoid, or waxy. Example: Cryptococcus
  • Mould or Filamentous Fungi: Multicellular, made of intertwined branching hyphae, reproducing via spores. Grow by longitudinal extension.
  • Dimorphic Fungi: Can grow as either a yeast or mould depending on environmental conditions and temperature. Example: Histoplasma capsulatum (mould at 25-30 °C, yeast at 35-37 °C)

Superficial Mycoses

  • Infections confined to the outermost layers of skin, hair, nails and mucosa
  • Examples:
    • Pityriasis versicolor: caused by Malassezia furfur
    • Dermatophytosis (Ringworm/tinea): caused by Trichophyton spp, Epidermophyton spp, Microsporum spp.
    • Candidiasis

Subcutaneous Mycoses

  • Involve the deeper layers of the dermis and subcutaneous tissue
  • Usually acquired from soil or thorns at sites of trauma.

Systemic Mycoses

  • Infections that can spread throughout the body

Candida

  • Normal flora of the mouth, intestine, and lower genital tract
  • Opportunistic pathogen, often in immunocompromised patients
  • Causes superficial (skin and mucosal) and systemic infections

Aspergillosis

  • Caused by Aspergillus, a mould found in soil, air, plants, and decomposing organic matter
  • Can cause allergies, aspergilloma, and invasive aspergillosis.

Diagnosis of Fungal Infections

  • Clinical diagnosis: Based on characteristic clinical presentation and examination
  • Microscopy: Direct examination of samples using KOH to clear keratin
  • Culture: Growing fungi on selective media like Sabouraud agar
  • Antigen detection: Identifying fungal antigens in urine, serum, or other body fluids
  • Serology: Detecting antibodies against fungal antigens in serum
  • Histopathology: Microscopic examination of tissue samples
  • Radiology: Imaging techniques like X-rays, CT scans, or MRI

Risk Factors for Invasive Fungal Infections

  • Haematological malignancy
  • Haematopoietic stem cell transplant
  • Solid organ transplant
  • Neutropenia
  • Extremes of age
  • Abdominal surgery
  • Prolonged ICU admission
  • Central venous catheter
  • Use of broad-spectrum antibiotics
  • Renal failure

Fungal Structure

  • Fungi are eukaryotes with a cell membrane, cell wall, and sometimes a capsule.
  • The cell membrane is a phospholipid bilayer containing ergosterol.
  • The cell wall is composed of chitin and carbohydrates like β-d-glucan and mannans, providing rigidity.
  • The capsule, when present, is a polysaccharide that acts as an antiphagocytic virulence factor.

Classification of Fungi

  • Fungi are classified as yeasts, moulds, or dimorphic fungi.
  • Yeasts are unicellular fungi that reproduce by budding and form moist, mucoid, or waxy colonies.
  • Moulds are multicellular fungi made up of branching hyphae and spores.
  • Dimorphic fungi can grow either as yeasts or moulds depending on environmental conditions.

Different Types of Fungal Infections

  • Fungal infections are classified as superficial, subcutaneous, or systemic.
  • Superficial mycoses affect only the outermost layers of skin, hair, nails, and mucosa.
  • Subcutaneous mycoses involve deeper layers of the dermis and subcutaneous tissue.
  • Systemic mycoses spread throughout the body.

Superficial Mycoses Examples

  • Pityriasis versicolor is caused by Malassezia furfur and presents as patchy, pale brown/pink macules.
  • Dermatophytosis (Ringworm/tinea) is caused by dermatophyte fungi such as Trichophyton, Epidermophyton, and Microsporum.
  • Candidiasis is caused by Candida albicans, a yeast-like fungus.

Subcutaneous Mycoses Examples

  • Sporotrichosis is caused by Sporothrix schenckii and is commonly acquired from contaminated plant matter.

Systemic Mycoses Examples

  • Histoplasmosis is caused by Histoplasma capsulatum, a dimorphic fungus found in soil and bird/bat guano.

Systemic Fungal Infections: Candida

  • Candida is a normal flora in the mouth, intestines, and vagina.
  • It can cause superficial and systemic infections, particularly in immunocompromised individuals.
  • Candida infections can affect the skin, mucosa, and internal organs.

Systemic Fungal Infections: Aspergillus

  • Aspergillus is a mould found in soil, air, plants, and decomposing organic matter.
  • It can cause allergic reactions, infections like aspergilloma, and invasive aspergillosis.

Diagnostic Techniques for Fungal Infections

  • Diagnosis involves clinical observation, microscopy, culture, antigen detection, serology, histopathology, and radiology.

Risk Factors for Invasive Fungal Infections

  • Invasive fungal infections are more common in individuals with weakened immune systems and those who have undergone organ transplantation or chemotherapy.
  • Risk factors also include neutropenia, extremes of age, prolonged ICU admission, and broad-spectrum antibiotic use.

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Description

This quiz explores the essential aspects of fungi, including their eukaryotic nature and classification into different types such as yeasts and moulds. It also covers their structural features like the cell membrane, wall, and capsular attributes. Test your knowledge of fungal biology and characteristics with this engaging quiz.

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