Fungi

Question 1

What is the difference between the two mycoses (endemic vs opportunistic)?

Answer 1

Endemic: Infection caused by fungal pathogen that are restricted geographically.
- These are true pathogens that typically result in systemic infections in healthy individuals

Opportunistic: Infections caused by fungi that are not a true pathogen. They cause systemic infection in only immunocompromised patients

Question 2

What are examples of endemic fungi pathogens?

Answer 2

• Histoplasmosis
• Blastomycosis
• Coccidioidomycosis

Question 3

Describe Fungi in general

Answer 3

• Eukaryotic organism with a true nucleus
• Fungi nuclear membrane consists of ergosterol
• Fungi cell wall is made of chitin, mannan, and glucan
• strict aerobes or facultative anaerobes (except Bakers yeast and Brewers yeast)
• Less than 1% can cause disease in humans

Question 4

Of the two types of fungi that cause disease in humans the two forms are ___ and ___.

Answer 4

• Unicellular (yeast)

- Multicellular fillamentus (mold)

Question 5

Describe yeast

Answer 5

• Unicellular (spherical/ovoid)

- Divide by budding, binary fission, or pseudomycelium

Question 6

Describe mold

Answer 6

• Multicellular filaments (hyphae)
• Vegatative growing into substrate
• Aerial for spore production

Question 7

Describe Histoplasmosis

Answer 7

• “Ohio valley disease”
• Found in the soil (fertilized by bird or batt droppings)
• Conidia (spores and filament) particles are inhaled => evade mucosal barrier and transform to yeast phase. Transformation from Conidia to yeast is required for pathogenicity
• *speads through lymph system
• Can cause pneumonia, acute/chronic disseminated histoplasmosis (common in immunocompromised patients)

Question 8

Describe Blastomycosis

Answer 8

• Found in soil and decaying wood in the Mississippi River Valley and souther states, but extends into Canada
• Very similar to histoplasmosis
• Conidia particles are inhaled
• Large, thick walled yeasts
• Multiplies in lungs and causes pneumonia
• Granuloma develops

Question 9

Describe Coccidioidimycosis

Answer 9

• Valley Fever in AZ, So Cal, NM, and TX
• Found in the burrows of desert animals
• Enters via Arthroconidia which are highly infectious when inhaled. They transform to Spherules that are filled with hundreds of endospores
• *dimorphism is not temp dependent
• Can cause Desert rheumatism, Valley fever, disseminated coccidiodiomycosis, and chronic meningitis

Question 10

What are the treatment for pathogenic fungi?

Answer 10

• Polyenes - lipophilic- bind to cell wall ergosterol and forms channels
• Azoles - interfere with ergosterol synthesis