Unit 13 Flashcards
What are the general characteristics of fungi?
Eukaryotic cells. All have cell walls usually composed of chitin and glucan. Cell membranes have ergosterol instead of cholesterol. Most are aerobes, but some are facultative and very few are obligate anaerobes. In nature fungi are saprobes (decomposers). More and more fungal opportunistic infections are arising in people living with various forms of immunosuppression.
What are the role of spores?
REPRODUCTION. Many species raise up a fungal head. THROW spores.
Yeast vs. Mold morphology
Yeast are generally the form in humans. They are single cell and reproduce through asexual budding and divide by mitosis. Mold is the free living, multicellular, saprophytic form. They grow in long filaments called hyphae. A cluster of hyphae forms a mat called a mycelium. My have conidia or asexual reproductive elements. Both yeast and mold forms present dimorphic.
How are fungi diagnosed?
Empirical diagnosis, growth/culture (Sabouraud’s agar, ID/Susceptibility testing similar to bacteria), Microscopy (May digest keratin with KOH, seen in much larger eukaryotic cells, may see hyphae or spores), or Antibody/Antigen/Molecular Biology (Immunoflourescence, ELISA, PCR).
How are fungal infections classified?
By where they occur. Superficial, cutaneous, subcutaneous, systemic.
Superficial fungal infection
Non destructive, located on hair or skin. Tinea nigra are black patches on soles of hands or feet. Tinea versicolor is altered pigmentation, usually hypopigmentation.
Cutaneous
Dermatophytes that live on skin, hair and nails. They secrete keratinase which causes scaling of skin, crumbling of nails and loss of hair. Examples include Tinea corporis, Tinea cruris, Tinea pedis, Tinea capitis, tinea unguium, Tinea barbae, Tinea faciei, and Tinea manuum. You treat topically with imidazoles or griseofulvin orally.
Candida albicans is a cutaneous fungal infection.
Cutaneous
Dermatophytes that live on skin, hair and nails. They secrete keratinase which causes scaling of skin, crumbling of nails and loss of hair. Examples include Tinea corporis, Tinea cruris, Tinea pedis, Tinea capitis, tinea unguium, Tinea barbae, Tinea faciei, and Tinea manuum. You treat topically with imidazoles or griseofulvin orally.
Candida albicans is a cutaneous fungal infection.
What is oral thrush?
Patches of creamy white exudates with reddish base. Cause by a cutaneous infection of Candida albicans.
What is oral thrush?
Patches of creamy white exudates with reddish base. Cause by a cutaneous infection of Candida albicans. If you remove the exudate you get a red, bleeding sore surface. You treat with a swish and spit nystatin or amphortericin B or imidazole lozenges. Candida can also cause a superinfection post abx.
What is a subcutaneus fungal infection?
Deeper layers of skin, muscle and connective tissue.
What is a subcutaneus fungal infection?
Deeper layers of skin, muscle and connective tissue. Ex: Sporothrix shenckii-sporotrichosis or Rose Gardner’s Disease, presents with sin lesions and can be systemic in some cases. Treatment depends on spread.
What is chromomycosis?
A long term subcutaneous infection.
Describe as systemic fungal infection.
Spread through out the body. Often amphotericin B or itraconazole is treated. Candida can go systemic. Crytococcus neoformans (yeast, but not dimorphic) has a capsule that is inhaled into lung and goes systemic in immunosuppressed HIV/AIDs causing fungal meningitis. Other examples include histoplasmosis capsulatum, blastomycosis, dermatidis and cocoidiomycosis immitis.
What does treatment of fungal infections depend on?
The location. In general the problem is that you are treating a euk infection in a euk.
