Fungi

• What are the two major forms of fungi?

  Yeast(unicelluar) and moulds(multicelluar)
• What is the primary structural difference between the cell walls of fungi and bacteria?

  Fungi have a rigid cell wall made of chitin and/or cellulose, while bacteria have muramic acid and teichoic acid.
• What are the characteristics of hyphae in fungi?

  Hyphae are threadlike filaments that can be septate or non-septate.

  
• What are the key features of yeast growth and morphology?


  • Yeast reproduce by budding from a parent cell.
  • Colonies on solid media resemble bacterial colonies.
  • Broth cultures appear turbid.
  • Pseudohyphae can be found in tissues.
  • Chlamydospores may be formed.
• What are the growth characteristics of moulds?

  • Moulds form aerial and substratum hyphae.
  • Growth on agar plates is important for identification.
  • Aerial mycelium may bear reproductive structures.

  
• What are the three main types of infections caused by fungi?


  Infections, allergy, and toxicosis.
• What are the major clinical forms of superficial mycoses?


  • Piedra (black & white)
  • Pityriasis (Tinea) Versicolor
  • Dermatophytoses

  
• What are the genera of dermatophytes that cause dermatophytoses?

  Microsporum, Trichophyton, and Epidermophyton.

  
• How are dermatophytoses classified clinically?

  • Tinea capitis – scalp
  • Tinea pedis – foot
  • Tinea unguium – nails
  • Tinea barbae – beard hair
  • Tinea corporis – nonhairy smooth skin

  
• What is the method for identifying dermatophytes through direct tissue examination?

  Using a 10-20% KOH preparation for microscopy.

  
• What are the major clinical forms of subcutaneous mycoses?

  • Lymphocutaneous sporotrichosis
  • Chromomycosis
  • Fungal mycetoma (eumycotic mycetoma)

  
• What is the causative agent of lymphocutaneous sporotrichosis?


  Sporothrix schenckii.

  
• What is the primary treatment for subcutaneous mycoses?

  Itraconazole, Amphotericin B, Ketoconazole, and Terbinafine.
• What are the characteristics of systemic mycoses?


  • Lungs are usually the portal of entry.
  • May involve any internal organs, subcutaneous tissue, and skin.
  • Caused by dimorphic moulds.
  • Severity varies with inoculum and patient’s immune status.

  
• What is the causative agent of histoplasmosis?

  Histoplasma capsulatum.

  
• What are the predisposing conditions for opportunistic mycoses?

  Diabetic ketoacidosis, chronic renal failure, and treatment with cytotoxic drugs and steroids.
• What are the clinical presentations of zygomycosis?


  • Caused by thermotolerant saprophytes.
  • Inhalation into the nasal cavity.
  • Strong association with diabetic acidosis.
  • Can affect pulmonary and brain tissues.

  In immunosuppressed patients

  – Rhizopus

  – Rhizomucor

  – Mucor
• What is the most common pathogenic yeast?

  Candida albicans.
• What are the lab diagnosis methods for Candida infections?


  • Culture on BA, CA, SDA, CROMagar.
  • Gram stain showing Gram positive oval cells.
  • Germ tube test positive for C. albicans.

  
• What is the causative agent of cryptococcosis?

  Cryptococcus neoformans.
• What are the lab diagnosis methods for cryptococcosis?

  • Culture on BA, CA, SDA.
  • Gram stain showing Gram positive spherical cells.
  • India ink preparations showing large capsules.
• What are the antifungal agents used for local and systemic treatment?

  Local:

  • Nystatin (for Candida)
  • Miconazole

  
  

  Systemic:

  • Griseofulvin (for dermatophytes)
  • Flucytosine
  • Amphotericin
  • Econazole, miconazole, ketoconazole
• What are the types of toxic fungi and their effects?

  1. Mushroom poisoning (e.g., Amanita phalloides) can lead to death.

  2. Mycotoxicosis from ingestion of toxins (e.g., aflatoxin from Aspergillus flavus).
• What is allergic disease related to fungi?

  • Allergic aspergillosis can cause asthma (farmer’s lung).
• Fungi are susceptible to antibiotics.

  
  

  False
• several hyphae make up a ?


  mycelium
• Culture for dermatophytes

  Growth on Sabouraud dextrose agar – made selective by the addition of antibiotics
• What is keratomycosis


  mycotic ulcers of the cornea
• Which organisms are mostly associated with chromomycosis?


  Organisms mostly associated with chromomycosis are the dematiaceous(naturally pigmented fungi) eg. Cladosporium