Fungi
last authored: Feb 2010, David LaPierre
last reviewed:
Introduction
Fungi are eukaryotes, meaning they are not susceptible to bacterial-aimed antibiotics.
Clinically, fungi can be divided into endemic fungi (ie histoplasma in the southern US) or opportunistic fungi.
We are usually protected against fungi by cell-mediated immunity.
Fungi are eukaryotic, possessing a nucleus and other organelles. Their cell membrane contains ergosterol, similar to cholesterol. Unlike algae, they lack chlorophyll. Fungi reproduce both asexually and sexually.
Dimorphics
- blastomyces
- coccidioes
- sporothrix
- Aspergillis fumigatus
- Candida albicans
- Cryptococcus neoformans
- Dermatophytes
- Histoplasma capsulatum
- Malassezia furfur
- Pneumocystis jiroveci
Fungal Classification
Fungi are classified based on the structures they form during sexual reproduction. Fungi that do not form sexual structures are called deteromycetes.
Broadly, fungi can be classified as yeasts or molds. Some systemic pathogens are dimorphic, growing as a mold and producing infectious spores at room temperature and then growing as yeast at body temperature. This limits person-to-person spread.
Yeasts are usually unicellular and elongate to form chains of cells called pseudohyphae. Yeasts reproduce by budding to form daughter cells. Molds are multicellular, forming tubular structures called hyphae that may have cross walls (septate) or no cross walls (aseptate). Many hyphase form a mycelium, forming spores; some hyphae can fragment to form arthrospores.
Fungal Diseases
Fungi can cause disease by growing on body surface, by invading, by inducing allergic reactions, or by toxin production.
Immune Response to Fungal Infection
The immune response to fungi depends largely on phagocytosis.
Yeasts are swallowed, while big mycelia etc are subject to frustrated phagocytosis.
Antibodies and complement play not a very big role indealing with fungi.
Resources and References
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