Fungi Overview and Structure Quiz
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Questions and Answers

Which of the following is NOT a characteristic of superficial mycoses?

  • Caused by dermatophyte fungi
  • Can be diagnosed with skin scrapings
  • Involves deeper tissues and organs (correct)
  • Limited to outermost layers of skin, hair, and nails

    • What is the main causative agent of Pityriasis versicolor?

  • Trichophyton spp.
  • Malassezia furfur (correct)
  • Microsporum spp.
  • Candida albicans

    • Which of the following dermatophyte fungi is NOT associated with tinea infections?

  • Microsporum spp.
  • Trichophyton spp.
  • Malassezia furfur (correct)
  • Epidermophyton spp.

    • Which type of tinea infection affects the groin area?

    <p>Tinea cruris</p> Signup and view all the answers

    Which diagnostic method is commonly used for diagnosing dermatophytosis?

    <p>Skin scrapings with KOH microscopy</p> Signup and view all the answers

    What distinguishes yeast from moulds in their structure?

    <p>Yeast reproduces by budding, while moulds grow by extension from hyphae.</p> Signup and view all the answers

    Which of the following is a characteristic of dimorphic fungi?

    <p>They can grow as either yeast or mould depending on temperature.</p> Signup and view all the answers

    What is the main component of the cell wall in fungi?

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

    Which of the following fungi is known for reproducing by budding?

    <p>Candida albicans</p> Signup and view all the answers

    What is the primary function of the fungal capsule?

    <p>To act as an antiphagocytic virulence factor</p> Signup and view all the answers

    What type of organism are fungi classified as?

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

    What is the role of spores in moulds?

    <p>They represent the primary mode of reproduction.</p> Signup and view all the answers

    Which of the following factors can increase the risk of invasive fungal disease?

    <p>All of the above</p> Signup and view all the answers

    What is the primary characteristic of subcutaneous mycoses?

    <p>Involvement of deeper layers of dermis and subcutaneous tissue</p> Signup and view all the answers

    What is the most common clinical presentation of sporotrichosis?

    <p>Cutaneous/lymphocutaneous infection after skin contact with contaminated plant matter</p> Signup and view all the answers

    Which method is NOT used for diagnosing sporotrichosis?

    <p>Antigen detection in urine</p> Signup and view all the answers

    What environmental factors are associated with Histoplasma capsulatum?

    <p>Located in soil enriched with guano from birds and bats</p> Signup and view all the answers

    What is a significant risk factor for disseminated sporotrichosis?

    <p>Immunodeficiency conditions like HIV</p> Signup and view all the answers

    What are common precipitating factors for Candida skin infections?

    <p>Antibiotics and immunosuppression</p> Signup and view all the answers

    How are Candida mucosal infections typically diagnosed?

    <p>Swabs for microscopy and culture</p> Signup and view all the answers

    What is a key characteristic of Aspergillus as a pathogen?

    <p>It produces spores that can germinate into hyphae</p> Signup and view all the answers

    Which of the following is NOT a common treatment for Candida infections?

    <p>Antibiotics to eradicate fungi</p> Signup and view all the answers

    Which of the following clinical manifestations is associated with Aspergillus infection?

    <p>Allergic Bronchopulmonary Aspergillosis (ABPA)</p> Signup and view all the answers

    What is a common symptom of allergic broncho pulmonary aspergillosis?

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

    Which diagnostic technique is primarily used for identifying fungal infections?

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

    Which of the following is NOT a risk factor for invasive fungal disease?

    <p>Healthy pregnancy</p> Signup and view all the answers

    What is the main treatment approach for aspergilloma?

    <p>Surgery in some cases</p> Signup and view all the answers

    What is commonly detected in patients with allergic broncho pulmonary aspergillosis?

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

    What is an essential characteristic of invasive aspergillosis?

    <p>It involves invasion of blood vessels</p> Signup and view all the answers

    Which method is used for the clinical diagnosis of fungal infection?

    <p>Microscopy and culture</p> Signup and view all the answers

    What major complication may arise from underlying lung damage in patients with aspergilloma?

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

    What factor can precipitate Candida skin infections?

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

    Which of the following is not a treatment option for Candida infections?

    <p>Amphotericin B</p> Signup and view all the answers

    What is a common clinical manifestation of Aspergillus infection?

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

    Which of these infections is a possible invasive complication of Candida?

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

    How are mucosal infections caused by Candida typically diagnosed?

    <p>Swab for microscopy and culture</p> Signup and view all the answers

    Which condition is characterized by pale brown or pink macules on the skin, primarily affecting the trunk and neck?

    <p>Pityriasis versicolor</p> Signup and view all the answers

    What is the primary organism responsible for causing tinea infections?

    <p>Dermatophyte fungi</p> Signup and view all the answers

    Which part of the body is affected by tinea capitis?

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

    Which diagnostic method involves the use of KOH to clear keratin before microscopy?

    <p>Skin scrapings</p> Signup and view all the answers

    Which of the following tinea infections affects the nails?

    <p>Tinea unguinum</p> Signup and view all the answers

    What is the primary route of entry for Sporothrix schenckii in cutaneous sporotrichosis?

    <p>Entry through a break in the skin from contaminated plant matter</p> Signup and view all the answers

    Which clinical presentation is most commonly associated with Histoplasma capsulatum infections?

    <p>Chronic respiratory infection resembling tuberculosis</p> Signup and view all the answers

    What is a key diagnostic method for detecting Sporothrix schenckii?

    <p>Microscopic examination using KOH preparations</p> Signup and view all the answers

    Which of the following is NOT a risk factor for disseminated sporotrichosis?

    <p>Active smoking habits</p> Signup and view all the answers

    How does Histoplasma capsulatum evade the immune system?

    <p>Living intracellularly within macrophages</p> Signup and view all the answers

    What is a distinguishing feature of yeast fungi compared to mould?

    <p>Yeasts reproduce mainly through budding.</p> Signup and view all the answers

    Which of the following factors influences whether a dimorphic fungus grows as a yeast or mould?

    <p>Temperature and environmental conditions.</p> Signup and view all the answers

    What structural component of fungi provides rigidity to the cell wall?

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

    Which of the following fungi is known for having a unicellular structure?

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

    What is a primary function of the polysaccharide capsule in certain fungi?

    <p>To provide antiphagocytic properties.</p> Signup and view all the answers

    Which type of fungi primarily comprises clumps of intertwined branching structures?

    <p>Moulds or filamentous fungi</p> Signup and view all the answers

    Which of the following is NOT a common feature of fungi according to their classification?

    <p>All fungi can reproduce through budding.</p> Signup and view all the answers

    What feature differentiates yeast-like fungi from true yeasts?

    <p>Yeast-like fungi can form pseudohyphae.</p> Signup and view all the answers

    What is the primary symptom of allergic broncho pulmonary aspergillosis?

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

    Which imaging finding is characteristic of an aspergilloma?

    <p>Fluid filled cavity</p> Signup and view all the answers

    What is the first-line treatment for invasive aspergillosis?

    <p>Antifungal therapy</p> Signup and view all the answers

    Which of the following is NOT typically a risk factor for invasive fungal disease?

    <p>Regular exercise</p> Signup and view all the answers

    What laboratory assessment is commonly used to diagnose allergic broncho pulmonary aspergillosis?

    <p>High antibody titers in serum</p> Signup and view all the answers

    Which diagnostic technique is specifically mentioned as part of the assessment for fungal infections?

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

    What is a common laboratory finding in patients with aspergilloma?

    <p>Positive antibodies in serum</p> Signup and view all the answers

    Which statement best describes the nature of invasive aspergillosis?

    <p>It involves the spread of infection from a primary site to other organs.</p> Signup and view all the answers

    Which of the following conditions is characterized by an itchy, patchy rash primarily on the trunk and neck?

    <p>Pityriasis versicolor</p> Signup and view all the answers

    Which genus of dermatophyte is associated with tinea infections affecting the skin?

    <p>Microsporum spp</p> Signup and view all the answers

    What is the primary method used to confirm dermatophytosis after initial clinical diagnosis?

    <p>Microscopy of skin scrapings</p> Signup and view all the answers

    Which statement accurately describes the dermatophyte infections known as tinea?

    <p>Tinea infections are specific to certain areas of the body and depend on the body part infected.</p> Signup and view all the answers

    Which method is primarily used for the diagnosis of pityriasis versicolor?

    <p>Clinical appearance and Wood's Light examination</p> Signup and view all the answers

    What distinguishes the clinical presentations of sporotrichosis from other fungal infections?

    <p>It typically presents as an ulcer followed by a granulomatous nodule.</p> Signup and view all the answers

    Which environmental factor is most closely associated with the presence of Histoplasma capsulatum?

    <p>Soil enriched with particulates from bird or bat guano.</p> Signup and view all the answers

    What is the primary reason for the difficulty in diagnosing Histoplasma capsulatum infections?

    <p>It has a very low sensitivity rate in microscopy.</p> Signup and view all the answers

    What role do pre-existing health conditions play in the severity of sporotrichosis?

    <p>They can increase the risk of disseminated sporotrichosis.</p> Signup and view all the answers

    Which method of diagnosis for sporotrichosis provides the fastest results?

    <p>Microscopic examination with KOH.</p> Signup and view all the answers

    What is the primary diagnostic technique for mucosal infections caused by Candida?

    <p>Swab for microscopy and culture</p> Signup and view all the answers

    Which condition is NOT considered a part of invasive Candida infections?

    <p>Allergic bronchopulmonary aspergillosis</p> Signup and view all the answers

    Which clinical manifestation is typically associated with allergic aspergillosis?

    <p>Chronic sinusitis</p> Signup and view all the answers

    What is a common factor that can trigger Candida skin infections?

    <p>Use of immunosuppressive therapy</p> Signup and view all the answers

    What type of fungus is Aspergillus primarily classified as?

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

    Which structural component is found in the cell membrane of fungi that differentiates them from bacterial cells?

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

    What is the primary characteristic that differentiates dimorphic fungi from other types of fungi?

    <p>They can switch between yeast and mould forms based on environmental conditions.</p> Signup and view all the answers

    Which type of fungus primarily reproduces through the production of spores?

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

    Which of the following accurately describes hyphae in moulds?

    <p>Multicellular and interconnected branching structures.</p> Signup and view all the answers

    What role does the fungal capsule play in pathogenicity?

    <p>Acts as an antiphagocytic virulence factor.</p> Signup and view all the answers

    Which of the following fungi can have both yeast and filamentous forms?

    <p>Candida albicans</p> Signup and view all the answers

    What feature of fungal spores distinguishes them in terms of their reproductive function?

    <p>They serve as reproducing bodies of moulds.</p> Signup and view all the answers

    Which of the following accurately describes the general classification of fungi?

    <p>Fungi can be classified into yeast, mould, and dimorphic fungi.</p> Signup and view all the answers

    What laboratory technique is most consistently used for diagnosing fungal infections in clinical settings?

    <p>Culture and microscopy</p> Signup and view all the answers

    Which of the following populations has the highest risk for developing invasive aspergillosis?

    <p>Patients with neutropenia</p> Signup and view all the answers

    What is the typical clinical presentation of allergic broncho pulmonary aspergillosis?

    <p>Bronchospasm and wheezing</p> Signup and view all the answers

    What is the common imaging finding in patients with aspergilloma?

    <p>Fluid-filled cavity on CXR or CT</p> Signup and view all the answers

    In allergic broncho pulmonary aspergillosis, which blood test result is commonly elevated?

    <p>High IgE levels</p> Signup and view all the answers

    Which of the following is a contraindication for using antifungal agents in aspergilloma treatment?

    <p>Local lung damage</p> Signup and view all the answers

    Which diagnostic method relies on observing fungal elements directly from a patient sample?

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

    In patients with invasive aspergillosis, which organ is least likely to be affected by the spread of the infection?

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

    Study Notes

    Fungi

    • Eukaryotic organisms
    • Found worldwide, some are endemic to specific regions
    • Exist as non-pathogenic, primary pathogens, and opportunistic pathogens
    • Not susceptible to antibiotics
    • Can be classified into yeast, mould, and dimorphic

    Fungal Structure

    • Cell Membrane:
      • Phospholipid bilayer
      • Surrounds cytoplasm
      • Contains Ergosterol
    • Cell Wall:
      • Composed of chitin and carbohydrates (ß-d-glucan and mannans)
      • Provides rigidity
      • Antigenic
    • Capsule:
      • Present in some fungi
      • Polysaccharide
      • Antiphagocytic virulence factor

    Yeast

    • Unicellular, spheroid or ellipsoid
    • Reproduce by budding
    • Moist, mucoid, or waxy colonies

    Yeast-Like Fungi (e.g., Candida Albicans )

    • Grow as both yeast and elongated hyphae (pseudohyphae)
    • Reproduce by budding
    • Generally creamy white colonies

    Mould or Filamentous Fungi

    • Multicellular
    • Composed of intertwined branching hyphae
    • Grow by longitudinal extension
    • Produce spores

    Dimorphic Fungi

    • Can grow as yeast or mould depending on environmental temperature:
      • Moulds in the environment at 25-30°C
      • Yeasts in human tissues at 35-37°C

    Fungal Infections: Importance & Types

    • Increasing Cases: Result of vulnerable patients undergoing chemotherapy, transplantation, and immunomodulatory therapies

    • Better Manageability: Improved diagnostic techniques and new anti-fungal agents

    • Types of fungal infections:*

    • Superficial: Limited to outermost layers of skin, hair, nails, and mucosa

    • Invasive: Infections involving deeper layers of cutaneous tissues, subcutaneous tissue, and systemic spread

    Superficial Mycoses

    • Pityriasis Versicolor:
      • Caused by Malassezia furfur (filamentous fungus)
      • Presents as patchy rash with pale brown/pink macules and pale patches (common in darker skin)
      • Itchy, commonly affecting the trunk and neck
      • More prevalent in hot, humid climates
      • Diagnosed by clinical appearance, Wood's Light examination, and skin scrapings
    • Dermatophytosis (Ringworm/Tinea):
      • Skin infections caused by dermatophyte fungi
      • Three genera of dermatophytes: Trichophyton spp, Epidermophyton spp, and Microsporum spp
      • Acquired from humans, animals, or soil
      • Location of infection dictates the Tinea type (e.g., Tinea capitis (head), Tinea pedis (foot), Tinea unguium (nail))
      • Diagnosed by clinical appearance, skin scrapings/nail clippings, microscopy (using KOH), and culture on selective media (Sabouraud agar)

    Subcutaneous Mycoses

    • Sporotrichosis (Rose Pickers Disease):
      • Caused by Sporothrix schenckii (dimorphic fungus)
      • Initial ulcer develops into granulomatous nodule
      • Acquired at sites of trauma from contaminated soil or thorns
      • Clinical Spectrum:
        • Cutaneous/Lymphocutaneous: Most common, enters through skin breaks, commonly affecting the hand
        • Pulmonary: Inhalation of fungal spores
        • Disseminated: Spread to other organs (e.g., osteoarticular, CNS), risk factors include immunosuppression, COPD, HIV, alcohol excess
      • Diagnosis:
      • Microscopy (KOH), Culture (Sabouraud agar), Histopathology, tissue biopsy, sputum, and body fluids

    Dimorphic Fungal Infection – Histoplasma Capsulatum

    • Grows as moulds at 25°C and yeasts at 37°C
    • Not prevalent in Ireland, UK, or Europe, but found in North America
    • Found in soil, bird/bat guano, and caves
    • Clinical Presentation:
      • Asymptomatic
      • Acute/chronic respiratory infections mimicking TB
      • Disseminated infections (liver, lungs, spleen) in immunosuppressed patients
      • Fungus lives intracellularly in macrophages, evading the immune system
    • Diagnosis:
      • Antigen detection (urine, serum)
      • Culture (tissue, blood body fluid)
      • Histopathology
      • Microscopy
      • Serology

    Candida

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

    Candida - Skin Infections

    • Presents with erythrema, plaque-like lesions, satellite lesions
    • Found in warm, moist areas, skin folds (intertrigo)
    • Precipitated by antibiotics, steroids, pregnancy, and immunosuppression
    • Diagnosis: Clinical appearance, skin scrapings, swabs
    • Treatment: Topical Antifungal agents (Clotrimazole), Oral antifungals (Fluconazole)

    Candida - Mucosal Infections

    • Discrete white patches on mucosal surfaces (oral, vaginal, oesophageal (especially in HIV))
    • Diagnosis: Swabs for microscopy and culture
    • Treatment: Topical antifungals (Clotrimazole), Oral antifungals (Fluconazole)

    Candida - Invasive Infections

    • Candida bloodstream infection
    • Infective endocarditis
    • Peritonitis
    • Osteomyelitis
    • Arthritis
    • Endophthalmitis

    Aspergillus

    • Mould/filamentous fungus
    • Found in soil, air, plants, and decomposing organic matter
    • Common in hospital environments
    • Pathogenesis:
      • Allergy: Reaction to Aspergillus antigens (ABPA)
      • Spore-forming: Spores inhaled, germinate into hyphae, destruct blood vessels, and disseminate

    Aspergillus - Clinical Manifestations

    • Allergic Aspergillosis: Sinusitis, Allergic Bronchopulmonary Aspergilliosis (ABPA)
    • Aspergilloma: Found in damaged lungs (TB, CF, COPD)
    • Invasive Aspergillosis: Risk groups: neutropenia, transplants, HIV, Spread from primary site to other organs (liver, spleen, kidney, CNS)

    Allergic Bronchopulmonary Aspergilliosis (ABPA)

    • Hypersensitivity reaction, common in patients with asthma or cystic fibrosis
    • Presents with bronchospasm, obstruction, wheeze, cough, shortness of breath, fever
    • Diagnosed by high antibody titres in serum with fleeting CXR changes and eosinophilia with high IgE levels
    • Treatment: Steroids and/or Itraconazole

    Aspergilloma

    • Found in damaged lungs
    • May be asymptomatic, but can cause chronic cough and hemoptysis
    • Diagnosed by sputum, antibodies and CXR/CT Thorax findings
    • Treatment - Surgery in some cases, no role for antifungals

    Invasive Aspergillosis

    • Risk groups: neutropenia, transplantation, HIV
    • Spread from primary site to other organs (liver, spleen, kidney, CNS)
    • Invades blood vessels

    Diagnostic Techniques

    • Diagnosis: Based on clinical presentation, examination, and additional testing
    • Techniques: 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
    • Broad-spectrum antibiotics
    • Renal failure

    Fungi

    • Eukaryotic organisms
    • Can be harmless, primary pathogens, or opportunistic pathogens
    • Not susceptible to antibiotics

    Fungal Structure

    • Cell membrane: phospholipid bilayer surrounding cytoplasm, contains ergosterol
    • Cell wall: composed of chitin, β-d-glucan, and mannans, provides rigidity, acts as an antigen
    • Capsule: present in some fungi, composed of polysaccharide, prevents phagocytosis by immune cells

    Classification of Fungi

    • Yeast: unicellular, reproduces by budding
    • Mould (Filamentous Fungi): multicellular, composed of branching hyphae, grows by extending hyphae, produces spores
    • Dimorphic: can grow as either yeast or mould depending on environmental conditions and temperature

    Some Definitions

    • Hyphae: tubules made up of fungal cells linked end-to-end, grow from the tip of the tubules
    • Spores: reproductive bodies of moulds

    Importance of Fungal Infections:

    • Increasing number of vulnerable patients (e.g., chemotherapy, transplantation, immunomodulatory therapies)
    • Improved diagnostic techniques and new antifungal agents make fungal infections more manageable

    Types of Fungal Infections

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

    Superficial Mycoses

    • Pityriasis Versicolor: caused by Malassezia furfur, characterized by patchy rash, pale brown/pink macules, or pale patches, most common on the trunk and neck
    • Dermatophytosis (Ringworm/Tinea): skin infection by dermatophyte fungi (Trichophyton spp, Epidermophyton spp, Microsporum spp), acquired from humans, animals, or soil
    • Candidiasis: discussed in later lectures

    Pityriasis Versicolor

    • Diagnosis: clinical appearance, Wood’s Light, skin scrapings

    Tinea (Ringworm)

    • Infection site dictates the name (e.g., Tinea barbae, Tinea capitis, Tinea pedis)
    • Diagnosis:
      • Clinical appearance
      • Skin scrapings/nail clippings
      • Microscopy (KOH prep), culture on Sabouraud agar

    Subcutaneous Mycoses

    • Involves deeper layers of skin, acquired from contaminated soil or thorns

    Sporotrichosis (‘Rose Picker’s Disease)

    • Caused by Sporothrix schenckii, initial ulcer progresses into granulomatous nodule

    Sporotrichosis Clinical Spectrum:

    • Cutaneous/Lymphocutaneous: most common, enters through a skin break from contact with contaminated plant matter
    • Pulmonary: inhalation of fungal spores
    • Disseminated: spread to other body parts (e.g., osteoarticular, central nervous system)
      • Risk factors: Immunodeficiency, COPD, HIV, alcohol excess

    Sporotrichosis Diagnosis

    • Microscopy (KOH prep)
    • Culture (tissue biopsy, sputum, body fluid)
    • Histopathology

    Histoplasma capsulatum

    • Dimorphic fungus: mould at 25°C, yeast at 37°C
    • Found in soil, bird/bat guano, caves
    • Can be asymptomatic or cause respiratory infection mimicking TB
    • Disseminated infection in immunosuppressed individuals
    • Lives intracellularly in macrophages, evading the immune system

    Histoplasma capsulatum Diagnosis

    • Antigen detection (urine/serum)
    • Culture (tissue, blood, body fluids)
    • Histopathology
    • Microscopy (low sensitivity)
    • Serology

    Candida

    • Normal flora in mouth, intestine, and lower genital tract
    • Opportunistic pathogen with increasing importance
    • Causes superficial (skin, mucosa) and systemic infections

    Candida Skin Infections

    • Erythema, plaque-like lesions, satellite lesions
    • Occur in warm, moist areas, skin folds (intertrigo)
    • Precipitants: antibiotics, steroids, pregnancy, immunosuppression

    Candida Skin Infection Diagnosis and Treatment

    • Diagnosis: clinical appearance, skin scrapings, swabs
    • Treatment: topical antifungal agents (clotrimazole), oral fluconazole

    Candida Mucosal Infections

    • Discrete white patches on mucosal surfaces (mouth, vagina, esophagus)
    • Diagnosis: swabs for microscopy and culture
    • Treatment: topical (clotrimazole), oral antifungal (fluconazole)

    Candida Invasive Infections

    • Candida bloodstream infection
    • Infective endocarditis
    • Peritonitis, osteomyelitis, arthritis, endophthalmitis
    • Discussed in detail in the Introduction to Opportunistic Infections lecture

    Aspergillus

    • Mould (filamentous fungus)
    • Found in soil, air, plants, decomposing organic matter
    • Common in hospital environments (construction work)

    Aspergillus Pathogenesis

    • Allergy: reaction to Aspergillus antigens in atopic individuals (Allergic Bronchopulmonary Aspergillosis - ABPA)
    • Spore-forming: spores inhaled, germinate into hyphae, damage blood vessels, and disseminate

    Aspergillus Clinical Manifestations:

    • Allergic Aspergillosis: sinusitis, Allergic Bronchopulmonary Aspergillosis (ABPA)
    • Aspergilloma: fungal ball in damaged lung
    • Invasive Aspergillosis: invades blood vessels and spreads to other organs, discussed in the Introduction to Opportunistic Infections lecture

    Allergic Bronchopulmonary Aspergillosis (ABPA)

    • Hypersensitivity reaction, common in asthmatics and cystic fibrosis patients
    • Bronchospasm, obstruction, wheezing, coughing, shortness of breath, fever
    • Eosinophilia, high IgE, high antibody titres in serum
    • Fleeting chest X-ray changes
    • Treatment: steroids +/- itraconazole

    Aspergilloma

    • Occurs in damaged lungs (TB, CF, COPD)
    • Asymptomatic, chronic cough, hemoptysis
    • Sputum positive in 66%, antibodies positive in 70%, fluid-filled cavity on CXR/CT
    • Surgery in some cases, no role for antifungals

    Invasive Aspergillosis

    • Risk groups: neutropenia, transplant, HIV
    • Spread from primary site to other organs (liver, spleen, kidney, CNS)
    • Invades blood vessels
    • Discussed in detail in Introduction to Opportunistic Infections lecture

    Diagnostic Techniques for Fungal Infections:

    • Clinical presentation
    • Microscopy and culture
    • Antigen detection
    • Serology
    • Histopathology
    • Radiology

    Risk Factors for Invasive Fungal Infections:

    • Hematological malignancy
    • Hematopoietic 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

    Summary

    • Covered yeast, moulds, and dimorphic fungi
    • Detailed classification, morphology, and pathogenicity of fungi
    • Explored superficial, subcutaneous, and systemic fungal infections
    • Discussed Candida and Aspergillus infections
    • Treatment of fungal infections will be covered in the antifungal/antiviral lecture
    • Invasive fungal infections will be covered in the Introduction to Opportunistic Infections lecture.

    Fungi

    • Fungi are eukaryotes
    • Fungi are found globally, some fungi are endemic to specific locations
    • Fungi 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 and carbohydrates (β-d-glucan, mannans), chitin provides 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 (e.g. Candida albicans): 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: grow either as yeast or mould depending on environmental conditions and temperature (moulds in environment at 25-30°C, yeasts in human tissues at 35-37°C)

    Terms

    • Hyphae: tubules made up of fungal cells attached end to end, growth occurs by extending in length from the tip of the tubules
    • Spores: reproducing bodies of moulds

    Why is Fungal Infection Important?

    • More Cases: increasing number of vulnerable patients (chemotherapy, transplantation, immunomodulatory therapies)
    • More Manageable: better diagnostic techniques, new anti-fungal agents available

    Types of Fungal Infection

    • Superficial: limited to outermost layers of skin, hair, nails, and mucosa
    • Invasive: involves deeper layers of tissue
      • Subcutaneous: involves deeper layers of the dermis and subcutaneous tissue
      • Systemic: spread throughout the body

    Superficial Mycoses

    • Pityriasis versicolor: caused by Malassezia furfur (filamentous fungus), common patchy rash (pale brown/pink macules), more common in hot, humid climates
      • Diagnosis: clinical appearance, Wood's Light, skin scrapings
    • Dermatophytosis (Ringworm/Tinea): skin infection caused by dermatophyte fungi (three genera: Trichophyton spp, Epidermophyton spp, Microsporum spp).
      • Acquired from humans, animals, or soil
      • Location of the infection determines the specific name of the infection (e.g. Tinea barbae - beard, Tinea capitis - head, etc.)
      • Diagnosis: clinical appearance, skin scrapings/nail clippings, microscopy (KOH), culture on selective media (Sabouraud agar)

    Subcutaneous Mycoses

    • Involves deeper layers of the dermis and subcutaneous tissue
    • Acquired from soil or thorns at sites of trauma

    Sporotrichosis ('Rose Picker's Disease)

    • Caused by Sporothrix schenckii (dimorphic fungus)
    • Initial ulcer develops into a granulomatous nodule
    • Clinical Spectrum:
      • Cutaneous/Lymphocutaneous: Most common, enters through a break in the skin from contaminated plant matter
      • Pulmonary: Inhalation of fungal spores
      • Disseminated: Spread to other parts of the body (e.g. osteoarticular, central nervous system), risk factors include immunodeficiency, COPD, HIV, excessive alcohol consumption
    • Diagnosis: microscopy (KOH), culture (Sabouraud agar - tissue biopsy, sputum, body fluid), histopathology

    Dimorphic Fungal Infection - Histoplasma capsulatum

    • Grows as a mould at 25°C and a yeast at 37°C
    • Found in soil, bird/bat guano, caves
    • Clinical Presentation:
      • Asymptomatic infection
      • Acute/Chronic respiratory infection resembling TB
      • Disseminated, involving liver, lungs, spleen (in immunosuppressed patients)
    • Diagnosis: antigen detection (urine/serum), culture (tissue, blood, body fluid), histopathology, microscopy (low sensitivity), serology

    Candida (Pseudoyeasts)

    • Normal flora: mouth, intestine, and lower genital tract
    • Opportunistic pathogen (increasing importance)
    • Superficial (skin and mucosal) and Systemic Infections

    Candida - Skin Infections

    • Clinical Features: Erythema, plaque-like lesions, satellite lesions, warm, moist areas, skin folds
    • Precipitants: antibiotics, steroids, pregnancy, immunosuppression
    • Diagnosis: clinical appearance, skin scrapings, swabs
    • Treatment: topical antifungal agents (clotrimazole), oral fluconazole

    Candida - Mucosal Infections

    • Clinical Features: Discrete white patches on the mucosal surface (oral, vaginal, oesophageal (especially in HIV patients))
    • Diagnosis: swab for microscopy and culture
    • Treatment: topical (clotrimazole), oral antifungal (fluconazole)

    Candida - Invasive Infections

    • Candida bloodstream infection, infective endocarditis, peritonitis, osteomyelitis, arthritis, endophthalmitis

    Aspergillus

    • Mould/Filamentous fungus
    • Found in soil, air, plants, decomposing organic matter
    • Common in hospital environments (construction work)

    Aspergillus - Pathogenesis

    • Allergy: due to reaction to Aspergillus antigens in atopic individuals (Allergic Bronchopulmonary Aspergillosis - ABPA)
    • Spore-forming Organism: spores are inhaled, germinate to form hyphae, destruct blood vessels and disseminate

    Clinical Manifestations of Aspergillus

    • Allergic Aspergillosis: sinusitis, Allergic Bronchopulmonary Aspergillosis (ABPA)
    • Aspergilloma
    • Invasive Aspergillosis

    Allergic Bronchopulmonary Aspergillosis (ABPA)

    • Hypersensitivity reaction, common in asthma and cystic fibrosis patients
    • Clinical Features: Bronchospasm, obstruction, wheeze, cough, shortness of breath, fever
    • Diagnosis Eosinophilia, high IgE, high antibody titres in serum, fleeting CXR changes
    • Treatment: steroids +/- itraconazole

    Aspergilloma

    • Occurs in damaged lungs (TB, CF, COPD)
    • Clinical Features: asymptomatic, chronic cough, haemoptysis
    • Diagnosis: sputum positive in 66% of cases, antibodies positive in 70% of cases, fluid-filled cavity on CXR/CT Thorax
    • Treatment: surgery in some cases, no role for antifungals

    Invasive Aspergillosis

    • Risk Groups: neutropenia, transplant patients, HIV
    • Clinical Features: spread from primary site to other sites (liver, spleen, kidney, CNS), invasion of blood vessels

    Diagnostic techniques for Fungal Infections

    • 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

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