Fungi

• Fungi


  • Eukaryotic cells
  • Saprophytic (feed on decaying matter)
  • Chemoheterotrophic (use organic chemical substance as source of energy)
• Yeast


  • Require body temperature
• Mold


  • Require at least 25°C or room temperature
• Reproduction of fungi


  1. Sexual and asexual

  2. Reproduce because of spores

  3. Asexual spores are called conidia
• Mycology


  The study of fungi
• Types of fungi


  • Yeast (unicellular)
  • Molds (multicellular)
  • Fleshy Fungi (mushroom)
• Medically important phyla of fungi

  • Deuteromycota
  • Zygomycota (conjugation fungi)
  • Ascomycota (sac fungi)
  • Basidiomycota (club fungi)
  • Mitosporic
• Deuteromycota (Fungi Imperfecti)


  • Group of fungi that doesn't have a sexual cycle
  • Produce asexual chlamydospores, arthrospores and conidiospores
  • Includes organisms that cause ringworm and thrush
  • Source of cyclosporine, an immune suppressant drug

  
• Zygomycota (Conjugation Fungi)


  • Saprophytic mold (obtain foods from decaying or dead matter)
  • Reproduce asexually and sexually using thick-walled zygospores, which are tough, resistant spores
  • Includes black bread mold
• Ascomycota


  • Asci/ascus → special sac containing spores of fungi (Ascospores)
  • Includes Penicillium, Claviceps, Micromonospora, Histoplasma, Blastomyces
  • Ciclosporin - from Tolypocladium inflatum
  • Antibiotics Penicillium chrysogenum, formerly notatum, (penicillin) and Penicillium griseofulvum (griseofulvin)
  • Cheese - blue Roquefort, Gorgonzola, and Stilton, fermenting milk with Penicillium roqueforti. Camembert and brie cheeses by fermenting milk with Penicillium camemberti
• Basidiomycota or Club Fungi


  • Possess septate hyphae (branching, clump of hyphae is mycelium)
  • Forms basidospores
  • Includes edible and poisonous mushrooms
• Mitosporic


  • AKA imperfect fungi
  • The only fungal group without spores
  • Eg. Candia albicans, Coccidioides
• Dimorphic Fungi


  • Can grow either as a yeast or a mold depending on the condition
  • Eg. Coccidioides, Paracoccidioides, Penicillium, Sporothrix, Candida, Histoplasma
• Mycoses


  Chronic (long-lasting) infections because fungi grow slowly (2 weeks or moths or years)
• Four types of mycotic diseases

  • Hypersensitivity
  • Mycotoxicosis
  • Mycetismus
  • Fungal Infection

  
• Hypersensitivity


  Respiratory allergens/aero allergens → asthmatic attack, skin rashes
• Mycotoxicosis


  • Ingestion of fungal toxin (contaminated food or product)
  • E.g. Ergotoxin → wheat with Claviceps purpurea
  • Claviceps purpurea may produce toxin that is carcinogenic
  • Ergotism - long-term ergot poisoning

  
• Mycetismus


  • Ingestion of poisonous fungi (from poisonous mushroom)
  • Toxins - amatoxins, phallotoxins, and virotoxins
  • These toxins inhibits the RNA polymerase which is needed in the transcription & translation when we produce amino acid that will make proteins

  
• Classes of fungal infections

  • Superficial mycoses
  • Cutaneous mycoses
  • Subcutaneous mycoses
  • Systemic mycoses
  • Opportunistic mycoses
• Superficial Mycoses


  • Most common infections in humans
  • Invades skin, hair and nails
  • Arthrospores adhere to keratinocytes, germinate and invade
• Black Piedra


  • Fungi on the hair strand
  • Aka Trichomycosis nodosa
  • Causative Agent: Piedraia Hortae
  • Symptoms: Black nodules on hair shafts
• White Piedra


  • Causative Agent: Trichosporon beigelii
  • Symptoms: Beige nodules on hair shafts
  • Something to do with hygiene
• Pityriasis Versicolor


  • Aka Tinea versicolor
  • Causative Agent: Malassezia furfur
  • Symptoms: hypo or hyperpigmentation
• Tinea Nigra


  • Causative Agent: Phaeoannellomyces werneckii, Exophiala werneckii
  • Symptoms: silver-nitrate like stains in the palm of hands or soles of foot (high keratin in palm of hands or soles of foot, silver-nitrate stain the skin for 2 weeks)
• Cutaneous Mycoses


  • Dermatomycoses (Candida albicans)
  • Dermatophytoses (Ringworms - Tinea Infections)
• Mucocutaneous Candidiasis


  • Oral thrush (white, cottage cheese like deposits)
  • Vaginitis (same with oral thrush)
  • Diaper rash (fungal infection of macerated skin(sweat))
• Dermatophytoses (Ringworms - Tinea Infections)

  • Epidermophyton (skin and nails)
  • Microsporum (skin and hairs)
  • Trichophyton (skin, hairs and nails)
• Dermatophytes


  Cause infection of the skin, hair and nails due to their ability to obtain nutrients from keratinized material
• Types of Tinea (Ringworm) Infections

  • Tinea capitis (affects the hair and skin of the scalp)
  • Tinea corporis (affects the body (trunk))
  • Tinea axillaries (affects the armpit)
  • Tinea manuum (affects the hands)
  • Tinea pedis (interdigital spaces on feet)
  • Tinea cruris (infection of the genital area or groin commonly called 'jock itch')
  • Tinea barbae (affects the area of the beard)
  • Tinea unguium or onychomycosis (infection of the toenail or fingernail)
  • Tinea Faciei (aka "tinea incognito" occur in the non-bearded area of the face)
• Symptoms of Cutaneous Mycoses

  • Annular scaling patch with raised margin
  • Itching – main symptom
  • Skin is often dry and scaly and sometimes cracks (between the toes in tinea pedis)
  • Hair loss
• Diagnosis of Cutaneous Mycoses

  1. Microscopic examination for fungal hyphae, use of KOH

  2. Culture on Sabouraud agar of scrapings or clippings from lesions (growth may take up to two weeks)
• Treatment of Cutaneous Mycoses

  • Topical azole
  • Keratolytic Whitfield's ointment (Salicylic acid)
  • Oral griseofulvin

  
• Subcutaneous Mycoses


  • Penetrate below the skin to involve the subcutaneous, connective, and bone tissue
  • Lesions develop at the sites of trauma (thorn, a bite) where fungus becomes implanted
• Major Forms of Subcutaneous Mycoses

  • Chromoblastomycosis
  • Mycetoma
  • Sporotrichosis
  • Phaeohypomycosis
• Chromoblastomycosis


  • Causative Agents: Fonsecaea pedrosoi , Phialophora verrucosa, Cladosporium carrionii, Fonsecaea compacta
  • Chrome-plated (Copper-pennies like lesions in the lower exremeties)
  • Limited only to the subcutaneous layer
• Mycetoma (Eumycetoma or Madura Foot)

  • Starts at subcutaneous → bone, cartilage and muscles
  • Malignant type
  • Carriers of melanin-like pigments
  • Causative Agent: Pseudallescheria boydii
  • Actinomycetes (caused by gram (+) bacteria)
• Sporotrichosis


  • Occupational disease of gardeners
  • Causative Agent: Sporothrix schenckii (saprophytic fungus)
  • Habitat: soil, on rose, tree bark
  • Infection acquired by trauma - occupation hazard for farmers, gardeners, and florists
  • Symptoms: nodules develops at the site of trauma followed by lymphatic spread
  • Diagnosis: culture of draining or aspirated material onto Sabouraud agar
  • Treatment: Oral Potassium Iodide
• Phaeohypomycosis


  • Characterized by presence of dark pigmented septate hyphae in subcutaneous tissues
  • Usually associated with immunosuppression
  • Might need surgery
  • Causative Agents: dark, melanin-pigmented dematiaceous fungi (Bipolaris,Cladophialophora, Cladosporium,Exophiala, Fonsecaea, Phialophora, Ochronosis, Rhinocladiella, and Wangiella)
• Systemic or Deep Mycosis

  • Infect internal organs i.e. blood, lungs,tissues, bone, meninges, brain
  • Often fatal
  • Infections: Aspergillosis, Blastomycosis, Candidiasis, Cryptococcosis, Histoplasmosis, Pneumonia(P.carinii)
• Primary Pathogens


  • Infect even immunocompetent
  • Coccidioides immitis (Clinical Manifestation: Coccidiodomycosis, aka Valley Fever, severe meningitis)