Mycology

• Mycology

  Study of fungi
• Fungi


  • Mushrooms
  • Molds
  • Yeasts

  
• Molds

  • Exhibit filamentous type of growth
• Yeasts


  • Exhibit pasty or mucoid form of fungal growth

  
• Fungi


  • Stain gram positive
  • Require oxygen to survive
  • Eukaryotic
  • Heterotrophic
• Two groups of fungi

  • Yeasts
  • Molds

  
• Yeasts


  • Single-celled organisms
  • Reproduce by budding process
• Molds


  • Produce hyphae, a long, hollow, branching filaments
  • Hyphae separate into compartments (septate)
• Dimorphic fungi


  Fungi capable of growing as yeasts at one temperature and as molds at another

  
• Uses of fungi


  • Development of antibiotic drugs like penicillin, streptomycin, and tetracycline
  • Development of cholesterol-lowering drugs (statins)
  • Yeasts used to make wine and beer
  • Saccharomyces cerevisiae used in baking
  • Algae and fungi used as a source of single-cell protein
  • Molds used to flavor cheeses
• Many diseases of crop plants, grains, corn, and potatoes are caused by molds
• Some molds and yeasts produce toxins (mycotoxins) that cause disease in humans and animals
• Molds and yeasts cause a variety of infectious diseases of humans and animals, collectively referred to as mycoses
• Fungi are not plants; they are not photosynthetic
• Fungal cell walls contain a polysaccharide called chitin
• Fungi


  • Some are unicellular, while others grow as filaments called hyphae
  • Hyphae intertwine to form a mass called a mycelium
  • Some have septate hyphae (divided into cells by cross walls or septa)
  • Some have aseptate hyphae (no septa)

  
• Fungal reproduction


  • Budding
  • Hyphal extension
  • Formation of spores

  
• Types of fungal spores

  • Sexual spores
  • Asexual spores (conidia)

  
• Fungal spores are very resistant structures

  
• Types of fungal infections

  • Superficial/cutaneous
  • Subcutaneous
  • Systemic

  
• Ringworm (Tinea)


  A common skin infection caused by a fungus
• Types of ringworm (Tinea)

  • Tinea pedis (athlete's foot)
  • Tinea unguium (onychomycosis)
  • Tinea cruris (jock itch)
  • Tinea capitis (scalp)
  • Tinea barbae (beard)
  • Tinea manuum (hands)
  • Tinea corporis (other body parts)
  • Malassezia (dandruff, seborrheic dermatitis)
• Diagnosis of fungal infections

  • Combination of microscopic and macroscopic observations
  • Immunodiagnostic procedures including skin tests

  
• Treatment of fungal infections

  • Antifungal agents (e.g. nystatin, amphotericin B)

  
• Preventive measures for ringworm

  • Wear clean shoes and slippers
  • Wash feet, hair, groin and face daily, dry well
  • Wear clean socks, clothing, towels and underwear
  • Change underwear and socks daily
  • Air out and wash sneakers regularly
  • Don't share personal clothing like towels
  • Take shoes off at home to expose feet to air
• Vaginal yeast infections (Candidiasis)


  Vaginal infection spread by the fungus Candida
• Candida


  • Organism that thrives on glycogen
  • Occurs more frequently during pregnancy
  • Most common in pregnant women with gestational diabetes and in women with HIV
  • Women using oral contraceptives or antibiotics are also susceptible
• Etiology of vaginal yeast infections

  • Disruption of normal flora, lack of Lactobacilli or antibiotic use
  • Can occur when pH of vagina is above 5
  • Late pregnancy may cause the fungus to propagate due to hormone shifts altering environment in vagina

  
• Clinical signs and symptoms of vaginal yeast infections

  • Candida-"CHEESE" discharge
  • White "patches" on vaginal walls that are adherent and cannot be scraped away without bleeding
  • Thick, cream cheese-like discharge
  • Pain on coitus or tampon insertion
• Oral candidiasis (oral thrush)


  Candida infections may also be present in the oral cavity or other moist areas, and can become systemic in immunosuppressed individuals
• Diagnostic tests for vaginal yeast infections

  • Microscopic examination of vaginal discharge with KOH solution
  • At-home pH test kit (Vagisil Screening Kit)
• Treatment of vaginal yeast infections

  • Antifungal therapy (e.g. nystatin, azoles)
• Nursing interventions for vaginal candidiasis

  • Health education on contributing factors
  • Ensuring medical compliance
  • Treatment of partners
• Histoplasmosis


  Also known as "Cave's Disease", caused by the dimorphic fungus Histoplasma capsulatum
• Histoplasmosis


  • Transmitted via inhalation of spores from soil contaminated with bat guano or bird droppings
  • Most cases are asymptomatic, some may cause acute pulmonary histoplasmosis
  • Worldwide distribution, generally low risk for travelers except when exposed to bird/bat droppings
• Treatment of histoplasmosis


  • Mild cases don't require treatment
  • Severe or chronic/disseminated cases require antifungal drug treatment for 3 months to 1 year
• Aspergillosis


  Caused by the common mold Aspergillus, affects people with weakened immune systems or lung diseases
• Symptoms of allergic bronchopulmonary aspergillosis (ABPA)


  • Wheezing
  • Shortness of breath
  • Cough
  • Fever (rare)
• Treatments for invasive aspergillosis


  • Voriconazole (first-line)
  • Alternative treatments: lipid amphotericin formulations, posaconazole, isavuconazole, itraconazole, caspofungin, micafungin
• Prophylaxis against aspergillosis is recommended for high-risk patients