Introduction to Mycology

• Health


  Wellbeing including all aspects of a person; physically, emotionally, mentally, and spiritually
• Causes of diseases


  • Genetic/Intrinsic
  • Acquired/Extrinsic
• Acquired causes of diseases

  • Physical
  • Chemical
  • Nutritional
  • Infectious
• Infectious causes of diseases

  • Bacterial
  • Parasitic
  • Fungal or mycotic
  • Viral
• Phenotypic diagnosis


  Uses characteristics of the specimen to identify the etiology of the disease, not specific and requires several pieces of evidence
• Genotypic diagnosis


  Uses molecular methods by identifying the specific DNA of a specimen, more accurate and faster identification
• Mycology


  The study of eukaryotic fungi, their structure, identification, and diseases caused
• Characteristics of fungi


  • Eukaryotic with true nucleus and mitochondria
  • Lack chlorophyll
  • Must absorb nutrients from the environment (heterotroph)
  • Nonmotile
• Fungi are capable of causing superficial, cutaneous, subcutaneous, or systemic disease
• Most fungi are obligate aerobes that grow best at a neutral pH, although they tolerate a wide pH range
• Moisture is necessary for growth but fungi can survive in any conditions for extended periods of time
• Medically important structures of fungi

  • Cell wall
  • Cell membrane
• Cell wall


  Stratified structure made up of chitin and carbohydrates, site of action for some antifungal drugs
• Cell membrane


  Rich in sterol (ergosterol), site of action for Amphotericin B and Azoles
• Types of fungi


  • Yeast
  • Mold
• Yeast


  • Unicellular, grows at 37°C, smooth creamy bacterial-like colony without aerial hyphae
• Mold


  • Multicellular, grows at 22°C, fuzzy and woolly appearance with aerial mycelia
• Components of molds


  • Hyphae
  • Spores
  • Rhizoid
• Hyphae


  Septate (with transverse walls) or aseptate (without walls), hyaline (lightly pigmented) or dematiaceous (highly pigmented with melanin)
• Spores


  The main reproductive units for fungi, used for identification based on arrangement and shape
• Rhizoid


  Root-like structure that anchors the fungus to the substrate, releases digestive enzymes and absorbs organic material
• Dimorphic fungi


  Assume both yeast and mold forms, temperature dependent
• Medically important dimorphic fungi

  • Histoplasma capsulatum
  • Blastomyces dermatitidis
  • Coccidioides immitis
  • Paracoccidioides brasiliensis
  • Sporothrix schenckii
  • Talaromyces marneffei
• Granuloma production


  Giant cells that arrange concentrically forming a round structure, found in diseases like coccidioidomycosis, histoplasmosis, blastomycosis
• Acute suppuration


  Accumulation of pus leading to tissue destruction, found in diseases like aspergillosis, sporotrichosis
• Delayed hypersensitivity skin test

  Fungal antigen injected intradermally, (+) induration indicates previous infection, (-) no induration may indicate immunocompromised state
• Transmission and geographic location

  • Habitat: Environment
  • Mode of transmission: Inhalation/Trauma
  • Systemic spread: Lungs to other organs
  • Point of entry: Respiratory system
  • Location: Endemic worldwide
• Host defenses


  • Intact skin
  • Bacterial normal flora
  • Respiratory tract
  • Humoral immune system
  • Cell-mediated immunity
• Fungal toxins and allergies

  • Mycotoxicoses (Amanita, Claviceps, Aspergillus)
  • Allergies (Type I hypersensitivity reaction)
• Classification of fungi (taxonomy)

  • Zygomycota
  • Ascomycotina (Ascomycota)
  • Basidiomycotina
  • Deuteromycotina (anamorph)
• Classification of fungi (by infection)

  • Superficial
  • Cutaneous
  • Subcutaneous
  • Systemic
  • Opportunistic
• Zygomycetes


  • Terrestrial fungi with coenocytic, aseptate hyphae
  • Asexual spores: sporangiospores
  • Sexual spores: zygospores
• Ascomycetes


  • Mostly terrestrial, saprophytes or parasites
  • Septate hyphae
  • Sexual spore: ascospore
  • Asexual spore: conidia
  • Teleomorph: sexual, Anamorph: asexual
• Basidiomycetes


  • Important contributors to ecosystem functioning
  • Rarely cause disease in humans
  • Diagnostic feature: club-shaped basidium
  • Sexual spore: basidiospore
• Deuteromycetes (Imperfect Fungi)


  • Saprophytes and parasites, some unicellular and others multicellular
  • Without sexual reproduction
  • Asexual spore: conidia
• Superficial fungi


  • Exophiala
  • Malassezia
  • Piedraia
  • Trichosporon
• Cutaneous fungi


  • Epidermophyton
  • Microsporum
  • Trichophyton
• Subcutaneous fungi


  • Cladosporium
  • Exophiala
  • Fonsecaea
  • Pseudallescheria
  • Phialophora
  • Sporothrix
  • Wangiella
  • Xylohypha
• Systemic fungi


  • Blastomyces
  • Coccidioides
  • Histoplasma
  • Paracoccidioides
• Opportunistic fungi


  • Alternaria
  • Bipolaris
  • Curvularia
  • Dreschlera
  • Epicoccum
  • Fusarium
  • Helminthosporium
  • Nigrospora
  • Absidia
  • Aspergillus
  • Candida
  • Mucor
  • Rhizopus
  • Rhizomucor
  • Syncephalastrum