Beveled Slide Style

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INTRODUCTION TO MYCOLOGY
By
Dr. Emad AbdElhameed Morad
Lecturer of Medical Microbiology and Immunology
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• Fungi are eukaryotic organisms.
• Their cell wall consists of chitin.
• Their cell membrane contains ergosterol.

Eukaryotes (Fungi) Prokaryotes (Bacteria)
10-100 um 0.1-10 um
Nuclear membrane No nuclear membrane
multiple Single chromosome
Histones No histones
Mitotic division Binary fission
Organelles No organelles
Chitin Peptidoglycan
Ergosterol No ergosterol
80 S ribosomes 70 S ribosomes
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• Classification

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Morphological
Clinical
Systematic
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Fungal morphology
Yeast
Mold
Dimorphic
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• Oval or round cells that reproduce by budding to
  form blastospores.
• May form pseudohyphae (if blastospores remain
  attached to each other).
• Examples Candida, Cryptococcus.

Yeasts
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Budding yeast cells
Pseudohyphae
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• Also called filamentous fungi or mycelial fungi.
• Formed of filaments called hyphae.
• Hyphae interlace to form mycelium.
• Hyphae may be septate or aseptate.
• Reproduce by formation of conidia.
• Conidia may be unicellular (microconidia) or
  multicellular (macroconidia).
• Examples are dermatophytes aspergillus.

Molds
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Hyphae
Mycelium
Microconidia
Macroconidia
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• These fungi occur in two forms
• At the room temperature (22 degree), it appears
  as mold.
• In the body (37 degree), it appears as yeast
  cells.
• Examples Histoplasma Blastomyces.

Dimorphic fungi
At 22 degree
At 37 degree
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Clinical classification
Superficial mycoses
Cutaneous mycoses
Subcutaneous mycoses
Systemic mycoses
Opportunistic mycoses
Allergy mycetismus mycotoxicosis
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• Fungal infections confined to the stratum corneum
  without tissue invasion.
• Example Tinea versicolor caused by Malassezia
  furfur.

Superficial mycoses
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• Fungal infections that involve keratinized
  tissues as skin, hair, nail.
• Example Tinea caused by dermatophytes.

Cutaneous mycoses
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• Fungal infections that are confined to
  subcutaneous tissues without dissemination to
  distant sites.
• Example mycetoma (madura foot).

Subcutaneous mycoses
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• Also called endemic mycoses.
• Begin as primary pulmonary lesions that may
  disseminate to any organ.
• Caused by dimorphic fungi.

Systemic mycoses
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• Affect immunocompromised individuals
• Examples are
• Candidiasis caused by Candida albicans.
• Cryptococcosis caused by Cryptococcus
  neoformans.
• Aspergillosis caused by aspergillus fungus.
• Pneumocystis pneumonia caused by pneumocystis
  jiroveci in AIDS patients.

Opportunistic mycoses
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• Allergy occurs to fungal spores particularly
  those of aspergillus fungus.
• Example bronchial asthma.
• The fungal flesh itself is toxic.
• Example Amanita mushroom poisoning.

Allergy
Mycetismus
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• Example Aflatoxins produced by Aspergillus
  flavus which infects grains and peanuts. This
  toxin is hepatotoxic and cause tumors in animals
  and suspected of causing hepatic carcinoma in
  humans.

Mycotoxicosis
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• It is based on the type of fungal spores
• Sexual spores
• Asexual spores

Systematic classification
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Sexual spores

• Zygospores
• Fungi forming zygospores are called zygomycetes.
• Ascospores
• Ascospores are carried in ascus.
• Fungi forming ascospores are called ascomycetes.
• Basidiospores
• Basidiospores are carried on basidium.
• Fungi forming basidiospores are called
  basidiomycetes.

Deuteromycetes are fungi whose sexual spores are
unknown. But, they produce asexual spores.
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Zygospores
Ascospores
Basidiospores
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Asexual spores

• Blastospores
• Produced by budding of the yeast cells.
• Conidia
• Produced by molds.
• May be microconidia or macroconidia.
• Arthrospores
• Produced by fragmentation of hyphae.
• Chlamydospores
• Rounded thick walled spores produced by candida
  fungus.

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Blastospores
Microconidia
Macroconidia
Arthrospores
Chlamydospores
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Antifungal drugs

• Selective toxicity is very limited in antifungal
  drugs because fungi like human cells are
  eukaryotic.
• They are
• Amphotericin B
• Binds to the ergosterol in the fungal cell
  membrane.
• Used in severe systemic and opportunistic
  mycoses.
• Nephrotoxic
• Flucytosine
• Inhibit fungal DNA synthesis.
• Used in combination with amphotericin B to treat
  candidiasis and cryptococcosis.
• It causes bone marrow inhibition, liver affection
  and hair loss.

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• Azoles
• Like ketoconazle, fluconazole, itraconazole.
• Inhibit ergosterol synthesis.
• Used in local and systemic fungal infections.
• Inhibit synthesis of testosterone leading to
  impotence.
• Terbinafine
• Inhibit ergosterol synthesis.
• Used in treatment of dermatophytes.
• Griseofulvin
• Used in treatment of dermatophytes because it is
  concentrated in the keratinized tissues.
• Topical antifungal agents
• Nystatin for oral candidiasis
• Clotrimazole and miconazole. (broad spectrum)

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• Caspofungin
• New antifungal drug
• Inhibit fungal cell wall chitin synthesis
• Used in invasive fungal infections
• Slow intravenous infusion
• Minimal side effects

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GOOD LUCK