Mycology

Question 1

What target of fungi is useful for diagnosis AND is also a good target for drugs?

Answer 1

The Chitin cell wall

Question 2

What form is a fungus in if it is living in a human?

Answer 2

Yeast (single cellular) form

Question 3

What does it mean to be saprophytic?

Answer 3

It means fungi can recycle organic matter that can be used in different ways

Question 4

What are the two primary differences between animals and fungi?

Answer 4

• Chitin Cell Wall

- Ergosterol Membrane

Question 5

What is the Chitin cell wall made of?

Answer 5

• Repeating Chain of N-acetyl glucosamine
• ß-1,3 and ß-1,6 glucans
• Lots of mannols

Question 6

Do humans have an equivalent of ergosterol in our membranes?

Answer 6

Yes, cholesterol - this is where problems arise with sterol targeting drugs

Question 7

What are the two methods of reproduction for Fungi and what nomenclature is associated with these?
- what name is given to each of these modes of reproduction?

Answer 7

Asexual Reproduction = Budding
Conidia - Asexual Reproductive Elements

Sexual Reproduction = Ascospores
Spores - sexual Reproductive Elements

Question 8

What are the two basic morphologies of fungi?

Answer 8

• Yeasts (single cell)

- Mold (multi cell)

Question 9

What structure is key to the pathogenicity of fungi?

- how do they gain access and how do they maintain residence?

Answer 9

Hyphae (NOT pseudohyphae)

• Proteinase activity can allow for penetration of epthelial cells to get to basement membrane to bind COLLAGEN and lock itself into position

**Some just bind to fibronectin and stay outside

Question 10

Molds

• single or multicellular
• key structures?

Answer 10

Multicellular

• These develope HYPHAE that can become intertwined to forma Mycelium

Question 11

Hyphae

• Different Types
• Subtypes?
• Function?

Answer 11

**Hyphae = key to determining pathogenicity

We look to see if they are branched or unbranched etc.

2 Types:
Vegetative
- Works like a plant root

Aerial Types

1. Sporangia
2. Condidia

Question 12

Differentiate between sporangia and condidia?

Answer 12

Sporangia - release sexual reproductive stuff

Condidia - release asexual reproductive stuff
***Condidia are Key parts of using Hyphae to make a diagnosis

Question 13

What two structural forms of Hyphae can exist?

Answer 13

1. Non-septated (multinucleate)
2. Septated (may or may not be multinucleate)

**Another feature of hyphae that is good for diagnosis

Question 14

How does nutrient exchange occur in fungi that are septated?

Answer 14

Pores are formed in the septa that allow nutrients but not organelles through

Question 15

What are fungi called called that can exist as a yeast or as a mold?
- can this ability increase virulence?

Answer 15

Dimorphic Fungi can exist in either capacity

**This is a key virulence factor for some human pathogens

Question 16

What is the precursor to both hypha and pseudohypha?

Answer 16

Germ Tube

Question 17

What difference in morphology likely exists between a fungus that is growing on your skin and one that is growing under it?

Answer 17

37 ˚C is the key temperature for conversion from mold to yeast

*Most pathogenic fungi are dimorphic so on the skin they will be a mold and under it they will likely be a yeast

Question 18

What are the 3 most common problems associated with molds coming into contact with people?

Answer 18

1. Allergies
2. Mycotoxicoses (e.g. Mushroom poisoning)
3. Mycoses (true fungal infection)

Question 19

T or F: after invading, many fungi begin excreting toxins that cause irritation

Answer 19

False, no known toxins are involved in human infection by fungi

Question 20

What type of infection is most commonly generated by a fungus?

Answer 20

Sub-acute, self-limiting infections

**Usually they’re only bad in opportunisitic infections

Question 21

WHAT TYPE OF IMMUNE CELLS ARE MOLDS MOST SENSITIVE TO???

Answer 21

Neutrophils (**especially opportunistic infections)

T-cell immunity is of primary importance

**Antibodies may play a role in preventing re-infection but this is very limited

Question 22

T or F: similar to viral infections, our own immune cells cause most of the harm in fungal infections

Answer 22

True

Question 23

What do we treat fungi with when we want to use it to make a Dx?

• What is the purpose of this substance?
• what are we looking at when we do this?

Answer 23

10% KOH, gets rid of any human tissue in the sample

• Leaves behind cell wall (CHITIN) which of diagnostic value

Question 24

What are fungi cultured on?

• what are the parameters of this medium?
• why so specific?

Answer 24

Sabouraud’s Medium is typically used

• High [glucose]
• pH 5.6
• Low pH inhibits bacterial growth, because in most cases the bacteria outgrow the fungi

Question 25

What do yeasts form on agar? | - what about mold?

Answer 25

Yeasts - form bacterial-like colonies Molds - differentiated by morphology

Question 26

What is the issue with using serology to diagnose systemic infections?

Answer 26

There is a lot of cross-reactivity among fungus

Question 27

What are there fewer anti-fungal medications than anti-bacterials? - are they typically more toxic? - Why or why not?

Answer 27

Less because there are less targets They are typically more toxic because they are more similar to human cells

Question 28

If you have an immunocompromized patient what life-long medicine will they most likely need to be on?

Answer 28

Azoles

Question 29

Zygomycetes, Ascomycetes, Basidiomycetes, and Deuteromyectes are all what?

Answer 29

Funi

Question 30

How do we classify fungi?

Answer 30

* *on increasing disease severity - Superficial - Cutaneous - Subcutaneous - Systemic - Opportunistic

Question 31

Where are Subcutaneous Mycoses found? - common reservoirs? - how do they get there?

Answer 31

- Deeper Layers of Dermis or Bone - Soil and Vegetation (Rose bushes) - Often occur at sites of trauma (such as a rose bush)

Question 32

You get a systemic fungal infection anywhere from the S. California to West Texas. What is the 1st pathogen to suspect? - what is your 1st line of treatment?

Answer 32

Coccidioidomycosis - Causes VALLEY FEVER, MOSTLY FOUND IN THE HIGH DESERT PLAINS 1st - Fluconazole IV/PO or Itraconazole PO Backup = amphotericin B

Question 33

You live anywhere near the Mississippi river and you get sick with a fungal pathogen, what are the suspects? - what is your 1st line of treamtent

Answer 33

1. Histoplasmosis - Amphotericine B IV and Itraconazole PO 2. Blastomycosis - Itraconzole PO (mild) - Amphotericine B IV then Itraconazole PO (severe)

Question 34

You get sick anywhere in the east side of the country with a systemic fungal infection. What is the most likely suspect?

Answer 34

1. Bastomycosis if you are not in the Miss. river region

Question 35

T or F: the endemic Mycoses are mostly systemic

Answer 35

True

Question 36

How does histoplasma capsulatum conidia evade host defenses?

Answer 36

1. Can prevent Phagolysosome Acidification 2. Prevents Fusion of the Phagolysosome ***This is an importnant feature for dissemination

Question 37

T or F: Thrush, Vulvovaginal, and Perianal Candidias are examples of opportunistic mycoses.

Answer 37

True

Question 38

T or F: diabetes mellitus is a risk factor for getting yeast infections

Answer 38

True