Terms in this set (46)
5 divisions of Fungi
Eukaryotic, absorptive, zygotic meiosis, unicellular, Filementous
each of the branching filaments that make up the mycelium of a fungus.
the vegetative part of a fungus, consisting of a network of fine white filaments (hyphae).
a possible infection of immuno compromised patients
3 different morphological types of Fungi
Yeasts, Mould, Dimorphic Fungi
Unicellular, reproduce by budding
Filamentous morphology with each filament known as a hyphae. A mass of hyphae is called Mycelium.
Grows as a mould at 25-30C in an environmental or saprophytic phase. At higher temperatures like 35-37C they are in the tissue or parasitic phase and grow as yeasts. Yeasts in the tissue or parasitic phase is the infectious form.
An increase in vegetative mass, involves development of asexual reproductive structures and known as the anamorphic state of fungus (the most clinically relevant)
Telomorphic state of fungus. Not usually clinically relevant.
5 divisions of fungi based on telomorphic characteristics
Chytidiomycota (NOT MEDICALLY IMPORTANT)
zygomycota, produce sexual spores
ascomytoca, produce sexual spores
Basidiomycota, produce sexual spores
Fungi imperfecti (deuteromycetes, large group of moulds in this class that cause disease)
Production of Sporangiophores which carry a Sporangium containing many sporangiospores
in the asexual phase
Production of Zygosporangium containing many zygospores in the
Ascomycetes life cycle
Production of Conidiophores which carry Conidia (the spore structure).
Basidiomycetes Life cycle
Production of Basidiospores via
reproduction which are carried by basidiocarp structures (mushroom caps).
1. Sporangiospores which are contained in a sac-like structure called a sporangium. FOUND EXCLUSIVELY IN ZYGOMYCETES.
Carried by structures known as a Sporangiophore.
2. Conidia, general term for spores of anamorphs other than those in the Zygomycetes.
Carried by structures known as Conidiophores
Sporebearing structures (sexual structures)
Ascomycetes: asci, cleistothecia
Basidiomycetes- basidocarps (mushrooms).
Specialized yeast structures
Chlamydoconidia (survival or resting conidia)
Candida albicans (harse conditions)
A negative stain for visualizing cryptococcus neoformans in CSF. Produces a polysaccharide capsule making it difficult to be ingested by macrophages and results in severe menigitis.
10 or 20% KOH
Helps with visualization of yeasts and hyphae in skin scrapings.
Suitable for yeasts and bacteria. Does NOT stain moulds.
Nonspecific fluorescent dye that binds to chitin.
Specific fungal media low yeild
Sabourad dextrose agar (SDA) with or without chloramphenicol and cycloheximide
Potato dextrose agar (PDA) for mould sporulation.
Inhibitory mould agar (AMA)
Fungal Media HIGH YEILD
Brain-heart infusion agar with sheep RBCs (BHI) enriched for cultivation of dimprphic fungi. (IMPORTANT)
Birdseed agar- Caffeic acid agar for Cryptococcus nneoformans. (IMPORTANT)
Very important fungi growth factors
Incubation temperature and time:
25C and 35C
Rapid (1-2 days) vs slow growth (2-4 weeks)
Germ tube test
Important identification technique for yeasts and allows for the rapid identification of Candida albicans.
e.g. Aspergillus spp., Penicillium spp
cross-walls are sparse or absent (coenocytic).
e.g. Mucor spp., Rhizopus spp
Lightly colored hyphae of MOULDS
Dark production of fungi colonies on solid media which form darkly colored hyphae.
Fungal infections, can be clasified as:
1. superficial (cutaneous) mycoses,
2. subcutaneous mycoses,
3. systemic mycoses (often start as pulmonary infection with dimorphic fungi, or opportunistic fungal infections).
Screens out UV light which will result in hypopigmented skin areas.
Superficial Tinea infection
Subcutaneous fungal infections
Dimorphic pathogenic fungi.
most common are:
1. Histoplasma capsulatum
2. Blastomyces dermatitidis
3. Coccidioides immitis
4. Paracoccidioides brasiliensis
Pathogenesis of fungal infections
morphological adaptation (dimorphism).
Resistance to phagocytosis and modulation of immune response.
Growth at 37C is the most pathogenic factor.
Immunity and Susceptibility to fungal infections
Innate or nonspecific barreris (skin, mucociliary clearance, alvorlar macrophges, PMNs).
Specific (humoral and cell mediated immunity).
Predisposition to fungal diseases: immunosuppresive therapy, immunocompromised individuals due to disease, broad--specturem antibiotics, Longterm catheterization, DM, neoplasms, hyperparathyrodism.
Topical medicals for superficial and cutaneous mycoses (dermatophytosis)
Desenex, Tinactin, Selsun lotion, Griseofulvin,
Acts as cytosine antagonists to inhibit nucleic acid synthesis (mostly RNA). Fungi have developed resistance.
May be combined with ampB for treatment of crypto neoformans.
Toxic side effects common esp bone marrow suppression.
Amphotericin B and nystatin.
Amphipathic (having both hydrophilic and hydrophobic motiffs) molecules that bind to ergosterol in fungal cell membranes . Disruption in membrane permeability leads to cell death. Can have host cytotoxicity since it acts on membranes.
Lipid associated forms of Amphotercin-B (versus amphotercin-B alone) have reduced toxicity allowing for higher dosing.
Amphotericin B Toxicity
Echinocandins and Terbinafine (lamisil)
Allylamine derivative that inhibits squalene epoxidase, essential enzyme for ergosterol synthesis.
Used for Topical or oral therapy for dermatophytic infections
Lipopeptides that inhibit synthesis of beta- (1-3)-D-glucan (essential for fungal cell walls)
Good choice for fighting Candida infections
Caspofungin (Cancidas), has activity against Candida and Aspergillus
Micafungin (Mycamine): Rx of Candida esophagitis in HIV patients
Anidulafungin: better activity than fluconazole against Candida spp.
Anti-fungals that prevent ergosterol synthesis due to inhibition of fungal cytochrome p450 enzymes and disrupting membrane integrity.
1. First generation azoles (imidazoles): Miconazole, clotrimazole for topical Candida skin infections.
Ketoconazole: IV use for Candida and dimorphic fungi.
A drug given that has hallucinogenic effects and also vasoconstrictive effects that can be administered to prevent postnatal bleeding.