Introduction to Mycology

Introduction to Mycology

• Mycology: The study of fungi.

  • Focuses on fungi's appearance, habitats, effects on humans, and their industrial applications (food, medicine).

Key Terms in Mycology

• Mycology: Study of fungi.

• Fungi: Eukaryotic organisms, more complex than prokaryotic bacteria.

• Saprophytes: Organisms that feed on dead organic matter.

• Mycosis: Fungal infections, a general term for infections caused by fungi.

• Mycotoxicosis: Illness caused by fungal toxins.

Morphology of Fungi

• Cell Structure:

  • Cell Membrane: Contains ergosterol; strengthens fungal cells.

  • Cell Wall: Made of chitin; provides shape and protection.

  • Capsule: Surrounds some fungi, helping evade the immune system.

  • Cytoplasm: Site of metabolic activities.

  • Nucleus: Contains DNA, controls cellular functions.

  • Endoplasmic Reticulum (ER): Synthesizes lipids/proteins

  • Golgi Apparatus: Packages and sends out substances in the cell.

  • Mitochondria: Generates ATP, the energy currency of cells.

Types of Fungi

• Molds: Multicellular fungi; produce spores through sporeulation and prefer neutral pH and room temperature (approx. 25°C).

  • Hyphae: Long, filamentous structures.

  • Septa: Walls within hyphae, dividing them into sections.

  • Mycelium: Dense network of hyphae.

• Yeasts: Unicellular fungi that reproduce by budding, thrive at body temperature (approx. 37°C).

• Dimorphic Fungi: Can exist as molds at 25°C and yeasts at 37°C (e.g., Histoplasma, Coccidioides).

Reproductive Strategies of Fungi

• Sexual Reproduction: Produces sexual spores (e.g., zygospores, ascospores, basidiospores).

• Asexual Reproduction: Produces asexual spores (e.g., conidiospores, sporangiospores, arthrospores, clamidospores).

Mycosis Classifications

Superficial Mycosis

1. Pityriasis Versicolor:

   • Caused by Malassezia furfur; results in white patches on skin.

   • Diagnosis: skin scraping.

2. Tinea Nigra:

   • Caused by Exophiala werneckii; presents with painless dark patches.

   • Treatment: topical imidazoles.

3. Black Piedra:

   • Nodular infection caused by Piedra hortae; affects hair shafts.

4. White Piedra:

   • Caused by Trichosporon beigelii; larger nodules on hair.

   • Treatment involves hair removal.

Cutaneous Mycosis

• Tinea/Ringworm:

  • Caused by dermatophytes; named after infected area (e.g., tinea pedis for athlete's foot).

  • Symptoms include red, itchy rings.

• Candida Albicans:

  • Opportunistic; causes oral thrush and vaginitis.

  • Treatment: nystatin (oral thrush) or topical medications (diaper rash).

Subcutaneous Mycosis

• Characterized by ulcerations and usually involves soil fungi.

1. Sporotrichosis:

   • Caused by Sporothrix schenckii; associated with gardening.

   • Treatment: oral potassium iodide.

2. Chromoblastomycosis:

   • Caused by Phialophora species; appears as cauliflower lesions.

   • Treatment: itraconazole or local excision.

Systemic Mycosis

• Fungal infections that affect the bloodstream.

1. Histoplasmosis:

   • Caused by Histoplasma capsulatum; transmitted from bird droppings.

   • Treatment: amphotericin B or itraconazole.

2. Blastomycosis:

   • Caused by Blastomyces dermatitis; respiratory symptoms.

3. Coccidioidomycosis:

   • Caused by Coccidioides immitis; causes flu-like symptoms.

Opportunistic Infections

1. Cryptococcus Neoformans:

   • Causes meningitis; diagnosis via ink stain of CSF.

   • Treatment: amphotericin B, flucytosine.

2. Pneumocystis jirovecii:

   • Leading cause of pneumonia in HIV patients.

   • Treatment: trimethoprim-sulfamethoxazole (TMP-SMX).

Conclusion

• Key Takeaways: Understand types of mycosis, their causative agents, and treatments.

• Encourage active engagement and questions for further clarity.