Mycology Flashcards
Are fungi eukaryotic or prokaryotic? What is the composition of their cell walls and what is the major membrane sterol?
Eukaryotic. Chitin, glucan and mannan makes up their cell walls (all carbs). Ergosterol is the major membrane sterol (instead of cholesterol for humans, thus this makes it a good target for anti-fungals).
What are the 3 things necessary for fungi to thrive?
They are all heterotrophic (requires organic carbon), Saphrophytic/saprobic (lives on dead organic material), and parasitic (can live on other living organism).
What is a “dimorphic fungi?”
It is a “mold in the cold, a yeast in a beast,” meaning the fungi has 2 forms: in the cold it is a mold and in warmer temp it is a yeast.
What are the 4 dimorphic fungi?
Histoplasma, Blastomyces, and Coccidioides (all 3 are systemic fungi), as well as Sporothrix (Sub Q fungal infection).
Mnemonic: Body Heat Changes Shape, (for Blastomyces, Histoplasma, Coccidioides, and Sporothrix).
What is the culture used to grow fungi and why is it this particular one?
Sabouraud’s agar, also called Sabouraud’s Dextrose agar. This particular culture inhibits bacterial growth so that bacteria does not overrun the parasite and use up all the nutrients.
What is the culprit in the disease “Tinea Versicolor” or “Pityriasis?” What kind of disease is this?
Malassezia Furfur. It is called versicolor because it can cause hypo (more common) or hyper pigmented skin, and this is an infection of superficial skin.
Describe the 2 ways Malassezia Furfur can present with disease.
It can cause hypo (or sometimes hyper) pigmented spots on the skin in the chest or back, by infecting the superficial keratinized cells. Warm moist conditions favor this (i.e. people who constantly work outside like construction people). It can also cause FUNGEMIA on premature infants that takes IV lipid supplements.
How would you diagnose Malassezia Furfur and what would you see?
Do a KOH mount of skin scales, you will see short round yeast, and curved septate hyphae, buzzword SPAGHETTI AND MEATBALLS KOH stain.
Can also use UV light to see a coppery/orange flurosence.
How do we tx Malassezia Furfur?
Selenium sulfide (found in anti-dandruff shampoo for example), and just rub on skin. However people who get this infection usually get it because their job requires they work outside in hot environments, so the infection can be recurrant.
What form are the dermatophytes found in and what do they infect?
They are always in the mold form, thus they are monomorphic. They infect the skin, hair and nails, but not necessarily all 3.
What are the 3 genera in the dermatophytes category of mycosis that causes cutaneous infections, and what do they infect?
Trichophyton (tri, infects all three hair skin and nails), microsporum (infects hair and skin) and epidermophyton (nail and skin). All three infect skin. however microsporum hits hair whereas the epidermophyton infects nails (think of “derm” including nails as well).
How does infection by dermatophytes present?
It can present with itching (very common) and inflammation (more inflammation if fungi comes from other species like cats and dogs, less inflamm if spread person to person).
What tinea infection causes permanent hairloss and is very infectious?
Tinea Favus.
What is the infection of the scalp by dermatophytes called? Of the beard? Of smooth skin without hair (glabrous)? Jock itch and athlete’s foot?
Tinea capitus is ringworm of the scalp, barbae is of the beard, corporis is of smooth hairless skin, cruris is jock itch and pedis is athlete’s foot.
How can microsporum be dx-ed?
Under UV “wood’s lamp” it will be a bright yellow/green.
