Microbiology-Mycoses Flashcards
What are the two categories of fungi?
Yeasts (single cell), Molds (multicellular)
Fungi are eukaryotes, however, their cell wall differs greatly from our plasma membranes. What is different?
Chitin (polysaccharide w/N-acetylglucosamine), glucans, and ergosterol (like cholesterol)
What is the primary target of anti fungal drugs?
Ergosterol in the cell membrane of fungi
How do most yeast replicate?
Budding
Instead of unique cells, how is mold structured?
Hyphal compartments continually grow outward.
How does fungal mold replicate?
Hyphae grow up from the mold and dissociate into spores.
How is fungal species determined?
Spore shape
How can you tell when a spore starts germinating?
Germ-tube.
How is fungus identified microscopically?
KOH dissolves surrounding cells so you can see fungus, silver staining and Calcofour white staining
What type of agar do you grow fungus on?
Sabouraud’s agar. It inhibits bacterial growth.
What are the three main anti fungal agents?
Azoles (ergosterol synthesis inhibitor), Polyenes/Amphotericin (binds ergosterol and forms pores), Echinocandins (inhibit beta-glucan synthesis for cell wall)
What immunity cells are key in preventing fungal infections?
Endothelial cells (recognizes beta-glucan’s dectin-1 and releases defensins), neutrophils, Th1 and Th17 cells.
How are fungus infections categorized clinically?
Superficial, Cutaneous, Subcutaneous, Systemic and Opportunistic
What yeast does Selsun Blue target?
Malassezia globosa
What yeast causes Pityriasis versicolor?
Malassezia furfur.
What disease culture can be enhanced by addition of oil?
Pityriasis versicolor
Pityriasis versicolor is not resolved unless treated. What treatments help resolve the infection?
Selenium shampoo or topical azole
A skin scraping shows this spaghetti and meatball appearance. What is the likely fungus?
Pityriasis versicolor
What are the common assailants of cutaneous mycoses?
Dermatophytes. The invade the stratum corneum, nails and hair.
What is this infection called?
Tinea capitis
What is this infection called?
Tinea pedis. Typically presents in moccasin distribution and desquamation.
How do you treat this infection?
Tinea unguium is treated with oral antifungals for months. Once fungal infections get into hair and nails you can’t use topical drugs anymore.
What type of fungal infections often require surgical interventions combined with medical treatments?
Subcutaneous mycoses. These are most often acquired by forced trauma.
What is the most common subcutaneous mycoses in the US?
Sporotrichosis
Your neighbor is out in her garden and is poked by a rose bush. A couple of weeks later she gets a nodule where she was poked. A few months later she has nodules with linear spacing up her arm. What is your diagnosis?
Sporotrichosis
How does the immune system respond to sporotrichosis?
Granuloma formation and eosinophils
You investigate a patient’s fungal infection by growing the fungus. You observe dematiaceous (pigmented) mold. What is the likely fungus?
Chromomycosis
Why is it important to differentiate eumycotic mycetoma from actinomycotic mycetoma?
Actinomycotic mycetoma can be easily treated with antibiotics and eumycotic mycetoma often requires amputation.
