Term
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Definition
Yeasts are single-cell organisms
Moulds are multi-cellular filamentous organisms
Fungi are found everywhere and tend to thrive in moist environments
About 150 species cause human disease |
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Term
| General Characteristics of Fungi |
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Definition
Are eukaryotic organisms
Lack chlorophyll
Are heterotrophic
Have cell walls made of chitin
Possess ergosterol as the major sterol in the cytoplasmic membrane
Tend to grow well in room air at an optimum temperature of 25-37°C in a moist environment |
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Term
| The Medical Importance of Fungi |
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Definition
Vaginal yeast infection, diaper rash, athlete’s foot
Predisposed to fungal infection:
Metabolic imbalances such as diabetes or pregnancy
Debilitating infections such as HIV
Neoplastic diseases such as leukemia, lymphoma or sarcoma
Immunosuppression with corticosteroids or cytotoxic drugs
Therapeutic measures such as radiation therapy
Administration of long-term broad-spectrum antibiotics |
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Term
| Fungal Structures of Moulds |
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Definition
The body or thallus is composed of long tube-like hyphae that produce a fluffy or fuzzy colony
Septate hyphae have cross-walls at regular intervals
Aseptate or nonseptate hyphae have no or very few cross-walls
Mycelium is the mass that develops as the hyphae grow
Vegetative mycelium anchor the mould colony
Aerial mycelium support the reproductive structures and provide the texture of the colony
Dematiaceous moulds have darkly pigmented hyphae
Hyaline moulds are nonpigmented
Begin as white and may produce color as the reproductive structures mature
Rhizoids are root-like strucutres that are part of the vegetative mycelium
Stolons are homologous to the runners of strawberry plants |
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Term
| Fungal Structures of Yeast |
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Definition
Discrete, round, smooth, moist, buttery colonies
Mother cell buds to form a blastoconidium
A chain of blastoconidia can form a filamentous-like pseudohyphae
Constriction visible between mother and daughter cells
Can produce germ tube from mother cell with no constriction
Some produce yeast or mould phases depending on temperature of growth |
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Term
| Asexual Reproduction in Fungi |
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Definition
Yeast form blastconidia
Mould form conidium or spore
Spores form on top of bottle shaped phalides that all sit on the enlarged end of stalk-like conidiophore
Septate hyphae, of some, enlarge and separate to become arthroconidia
Round chlamydoconidia, a large resting spore, can form on the end of hyphae (terminal) or within the hyphae (intercalary)
Zygomycetes
Spores are formed with a sac-like sporangium
Branched or unbranched sporangiophores, aerial hyphae, bear the sporangium
Sporangium contains sporangiospores
Round columnella forms at the tip of the sporangiophore and extends into the sporangium |
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Term
| Sexual Reproduction in Fungi |
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Definition
Gametes (n) fusion → zygote (2n) nuclear fusion → meiosis (n)
Does not occur in every species
Fungi Imperfecti or dueteromycetes
If an organism produces both sexual and asexual forms, each form is given a different genus/species name
Sexual form is called a teleomorph
Asexual form is called an anamorph
Ascomycetes, Basidiomyctes and Zygomycetes produce sexual and asexual forms
Ascomycetes have sexual spores encased in an ascus and produce ascospores
Basidiomycetes create basidospores on a stalk-like sterigmata (mushrooms)
Zygomycetes form a thick walled zygosporium containing a single zygospore |
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Term
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Definition
Fungi can abandon their saprophytic existence to cause opportunistic infections in those with:
HIV infection
Leukemia, lymphoma and cancer
A transplanted organ
Diabetes
Pregnancy
Aspergillus and Candida are most common |
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Term
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Definition
A. fumigatus is most common
Otomycosis, keratomycosis, pneumonia, sinusitis, skin ulcers and invasion of internal organs |
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Term
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Definition
Includes the genera Rhizopus, Mucor, Rhizomucor and Absidia
Known for infection in those with:
Immunosuppression
Lymphoma, leukemia
Malnourishment
Metabolic disorders
Trauma |
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Term
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Definition
Any disease caused by Rhizopus, Mucor and rarely Absidia
Normal in soil and decaying matter
Rhinocerebral, pulmonary, gastrointestinal, subcutaneous and disseminated disease
Inhalation of spores
common sites are sinuses and lungs
Rhinocerebral mucormycosis
Seen with uncontrolled acute diabetes mellitus, hyperglycemia, metabolic ketoacidosis and leukopenia
Begins in nasal sinuses and spread into orbit of eye, palate and brain
Has a preference for invasion of blood vessels |
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Term
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Definition
Most common cause is Fusarium solani
Noted for pink or lilac colonies
Other genera
Aspergillus, Acremonium, Pseudallerscheria boydii, Candida albicans, dematiaceous fungi such as Bipolaris, Curvularia, and Cladosporium spp.
Predisposing factors
Accidental ocular trauma, surgical ocular trauma, ocular topical corticosteroids and antibiotics
Farmers, fruit pickers, gardeners
Foreign object sensation with intensifying pain
Redness, corneal ulcer, pus in anterior eye chamber
Eventual loss of eye
Demonstrate fungi in tissue and on culture |
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Term
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Definition
Aspergillus niger, A. fumigatus, Candida spp. and Penicillium spp. are most common
Hearing loss, itching, pain, discharge
Fungal growth may be observed in ear canal |
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Term
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Definition
Involves outermost layers of skin or hair shaft
Pityriasis (Tinea) Versicolor
Chronic superficial skin infection
Often young adults in tropical areas
Found on upper back, shoulders, upper arms, chest and abdomen
Lesions are hypo- or hyperpigmented, scaly and itchy
Causative agent is Malassezia furfur
Part of normal skin flora |
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Term
| Superficial Phaeohyphomycosis or Tinea Nigra |
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Definition
Brown fungal infection
Chronic skin infection that is seen young adults in tropical areas
Single, black spot with a distinct border
Usually on hands, bottom of feet, neck or chest
Slight itching
Caustive agent is Hortaea werneckii
Dematiaceous or black fungus |
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Term
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Definition
Infection of hair shaft
Axilla, beard, mustache, scalp, genital area
White to tan nodules adhering loosely to the hair shaft
Mycelia grow inward and penetrate hair cuticle
Hairs may break off above nodule
Caused by Trichoporon beigelii (T. cutaneum) |
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