Fungi Flashcards
Why don’t antibiotics work on fungi?
Cell wall isn’t peptidoglycan (instead has a cell wall of chitin and beta glucan, an 80S ribosome
Do fungi survive/reproduce in oxygen? Are they heterotrophic or autotrophic?
Most are obligate aerobes, none are able to survive anaerobically; heterotrophic
Fungi are better at growing in these conditions than bacteria:
Colder, drier, more acidic, and higher osmotic pressure
What are the two types of fungi? How are they different? How do they reproduce?
Yeasts (single celluar, reproduce by budding); Molds (multicellular that grow as filaments known as hyphae, reproduces either sexually or asexually)
Mats of hyphae are called:
mycelium
How is closed mitosis different from open mitosis?
The nuclear envelope never breaks down in closed mitosis
What form of fungi predominately reproduces by closed mitosis?
Yeasts
According to thermal dimorphism what would a form would a fungi be in at 24C? At 37C?
24C mold, at 37C yeast
Fungi imperfecti reproduce primarily sexually or asexually?
Asexually
What are the two responses to fungi by the immune system?
Granuloma formation and acute suppuration (filling with pus)
What fungi are responsible for granuloma formation?
histoplasmosis, blastomycosis, coccidiomycosis
What fungi are responsible for acute suppuration?
aspergillosis and sporotrichosis
What are the consequences of fungi being environmental pathogens? (both positive and negative)
Not really contagious (non-communicable), no drug resistance, not able to be eradicated
What fungi is considered normal flora?
C. albincans
How do you get mycotoxicosis?
Eating fungal toxins (such as a the wrong mushroom or spoiled food)
How would you culture a fungal sample?
Treat with KOH (breakdown surrounding tissue), place on Sabourad’s agar (inhibits bacterial growth), look for appearance of mycelium or asexual spores
What are the major classes of antifungals and how do they work? (3)
polyenes: disrupt fungal cell membrane at ergosterol
azoles: inhibit ergosterol synthesis
echinocandins: inhibit beta glucan synthesis
How does amphotericin B work? What is it used for?
Targets ergosterol (forms a channel in membrane disrupting ions); used for broad range of systemic infections, only give when life threatening because has harmful side effects (toxic to major organs); give to pregnant patient with systemic mycoses
How does echinocandins work? What is it used for? Who can’t use it?
Inhibits synthesis of beta-glucan, low toxicity so good for systemic use, can’t use in pregnant women; used against candida and aspergillus
How do azoles work? What are they used for?
Bind to precursers of ergosterol so that ergosterol can’t be made; less toxic, flucoazole is a class that is useful against candida and cryptococcal
Name the four different classes of fungal infections
Superficial, subcutaneous, systemic, opportunisitc
Where are superficial mycoses found? What do they look like?
Superficial layer of skin, non-life threatening with discoloration/itching of the skin
What is the example used in lecture that produces superficial mycoses caused by?
Dermatophytes
What two fungal infections arise because the fungi is thermically dimorphic?
Subcutaneous and systemic
How are superficial mycoses treated?
Topical azoles or if hard to reach oral griseofulvin
How are superficial mycoses transmitted?
Contact with fomites and later autoinoculation, or from chronic infection in warm, humid areas of skin
What cells are targeted by dermatophytosis? How do they accomplish this?
Superficial keratinized cells– produce keratinases
How are superficial mycoses diagnosed?
KOH mount and culture
How are subcutaneous mycoses transmitted? Where does it go once in the body?
Enters the skin following some form of trauma so get get exposure to vegetation/soil- in the body is slowly spreads to trunk via lymphatics
How are subcutaneous mycoses treated?
Oral azoles- but in serious cases may require AmpC or surgery
Sporotrichosis causes what type of mycoses?
Subcutaneous
What might sporotrichosis look like in patients with COPD? Those that are immunosuppressed?
COPD: have pulmonary involvement
Immunosuppressed leads to disseminated and can cause meningitis
How is sporotrichosis diagnosed?
Take pus and culture
How are systemic mycoses transmitted?
Inhalation of fungi/spores from soil
What symptoms are associated with the inhalation of coccioides arthospores? Mild, moderate and severe
Mild:see asymptomatic/flulike clearance
Moderate: valley fever/desert rheumatism- pulmonary and erythema nodosm (rash on shins)
Severe: major pneumonia and dissemination
What does coccioides look like? How can you tell the difference by looking at history?
TB- TB is usually foreign, Cocciodies is from endemic soil in SW
How are coccioides treated?
If immunosuppressed, diabetic, or cardiopulmonary disease treat with oral azoles
If pregnant treat with Amp B
If have persisting lung lesions or disseminated mycoses then treat with Amp B
What is the optimal treatment for opportunistic mycoses?
Treats the pre-existing condition and the fungal infection
How is cryptococcosis transmitted? What are the outcomes?
Inhaled and goes to the lungs there either cleared and asymptomatic if healthy immune; if immunocompromised then pneumonia
What is the life threatening complication of cryptococcis in immunocompromised?
Meningitis
How is cryptococcis treated in the immunocompromised?
Combinations of AmpB and oral azoles
