L7: Introduction to Mycology Flashcards
Are fungi eukaryotic or prokaryotic?
Photosynthetic or nonphotosynthetic?
Eukaryotic
Nonphotosynthetic
Cell walls of fungi contain what? 2
Describe each
- Beta-glucans (D-glucose polymer)
2. Chitin (polysaccharide chain of NAG)
Plasma membranes of fungi contain what?
What do animal PM’s have?
Ergosterol
Cholesterol
Do Fungi use sexual or asexual reproduction?
Both
Are fungi haploid or diploid?
Both
Haploid = lower fungi
Diploid = higher fungi
Two forms of fungi? Define each
- Yeast: Single celled
2. Mold: Multicelliular
For molds, the principal element of vegetative growth is what?
Hypha
Hyphae in terms of structure can be categorized how? (2)
- Septate: Divided by partitions
2. Coenocytic: hollow and multinucleate
In terms of where they grow, how can hyphae be categorized?
- Aerial = Above surface and are reproductive
2. Vegetative = Below surface and absorb nutrients
How do yeast reproduce?
- Nuclear fission
2. Budding
What are colonies of masses of intertwining hyphae called?
Mycelia
Dimorphic fungi can do what?
Be a yeast or a mold depending on environment
When are dimorphic fungi a yeast?
Physiologic temperature and abundant nutrients
When are dirmophic fungi mold like?
Ambient temperatures and when conditions are not optimal.
When do dimorphic fungi produce spores?
When in mold-state
Do most fungi do sexual or asexual reproduction?
Most can do both
What is the basis for traditional fungal classification?
Sexual reproduction: Spores made and structures used
Mucormycetes or Zygomycetes form what in reproduction?
Hyphal fusion results in Zygospore
Describe a zygospore
Stalk of sporangiophore with sporangium on top in which haploid zygospores form.
Ascomycetes do what in sexual reproduction?
Neighboring segments fuse to form an ascus. Nuclei fuse, undergo meiosis, then mitosis to form ascospores
What group of fungi are the largest group of human pathogens?
Ascomycetes
Upon fusing together, what is the status of zygomycete ploidy?
Diploid
Basidiomycetes have what for sexual reproduction?
Basidiosporespores develop in basidium and migrate to surface before release
Deuteromycetes do what for sexual reproduction?
What are they similar to?
No sexual stage observed,
Most are similar to asomycetes
Asexual spores have what two names?
Sporangiospores
Conidia
What does it mean if spores are sporangiospores?
They are contained in a structure
What does it mean if spores are conidia?
Born naked on specialized structures
What two types of spores form by fragmentation of hyphae?
Differentiate the two
- Arthospores: Rectangular
2. Chlamydospores: Circular
Blastospores form how?
What form are they usually in?
By budding
Yeast
Five categories of pathogenic fungi?
Superficial Cutaneous Subcutaneous Systemic Opportunistic
Are most people resistant to pathogenic fungi?
yes
Resistance factors to pathogenic fungi include? (4)
- Fatty acids
- pH
- Epithelial cell turnover
- normal flora
Superficial mycoses have what effect?
Cosmetic, no physical discomfort
Superficial mycoses infect what?
Nonliving tissue
How do you treat superficial mycoses? 2
- Keratolytic agents
2. Shaving
Cutaneous mycoses are restricted to what tissues?
Keratinized tissues such as nails, hair, and stratum corneum
Most cutaneous mycoses are what type of parasites?
Obligate human parasites
Can cutaneous mycoses be transmitted person to person?
Yes
What is the collective name for cutaneous mycoses species
Dermatophytes
How does susceptibility vary for cutaneous mycoses? 2
- Demogrpahics of patient
2. Footwear and clothing
Cutaneous mycoses begin where?
How do they spread
Based on how they are spread, what are they called? 2
Cornified layer of skin
Ringworm or tineas
Cutaneous mycoses induce what? 2
Cellular respones and inflammation
What is the most fatal type of mycoses?
Subcutaneous mycoses
Two examples of subcutaneous mycoses?
Sporotrichosis
Chromoblastomycosis
How do you get a subcutaneous mycoses?
Trauma lets it in
What is Rose Gardener’s Disease?
When a rose thorn causes trauma allowing spores into subcutaneous tissue
Systemic mycoses are in what form at physiologic temperature?
At ambient temperature?
Yeasts
Molds
Systemic fungi live in what environments?
Specifically what types of habitats?
Alkaline
Bat and bird feces
How are systemic mycoses acquired?
What is the primary site of infection?
Inhalation
Lungs
What are most systemic mycoses symptoms?
Asymptomatic or mild
Systemic mycoses have a tendency to cause what?
Granuloma formation
How are systemic mycoses restricted?
By geography
Opportunistic mycoses require what?
A hampered immune system
Opportunistic mycoses will be seen when what happens? 6
- Debilitation
- endocrine problems
- Cancer of WBC’s
- Immunosuppression
- Antibiotics
- X-irradiation
Opportunistic mycoses are typically what?
Environmental saprophytes or normal body flora
Oral thrush is usually the result of what? (2)
- Long term antibiotic
2. Immunosuppression
Mycotoxins are seen in what two species?
- Amanita mushrooms
2. Aspergillus
Amanita mushroms make what two important hepatotoxins?
- Amanitin
2. Phalloidin
Aspergillus makes what?
How do you acquire this?
Aflatoxins
Eating spoiled grains and peanuts
Lab diagnosis of mycoses is done how?
Culture Microscope Immune response/Serology Examination of tissue samples Nucleic Acid PCR
What is the common medium for culture lab diagnosis?
What is the relative speed of fungi growth?
Sabouraud’s agar
Slow
What do you look for in tissue samples?
- Hyphae, yeast forms in tissue treated with KOH or special stains
- Antigen detection by ELISA
The telltale sign of fungus is what?
KOH treatment: destroys human tissue but doesn’t harm fungal
What are the fungal targets for drugs? 5
- Cell wall = inhibiting glucan synthesis
- Cell membrane = inhibiting ergosterol syn
- Cell membrane = damage
- Nucleus = Disruption of microbutules and inhibition of mitosis
- Nucleus = Inhibit nucleic acid synthesis
Polyenes in clude what?
Amphotericin B and Nystain
Polyenes target what and bind to this?
Ergosterol
Polyene binding to ergosterol cause what?
Produce ion channel that destroys osmotic integrity of cell membrane –> Death
Amphotericin B does what?
As a polyene, it binds to ergosterol, forms an ion channel, and disrupts potential.
Nystain does what?
Binds to ergosterol
How is nystain used?
Why?
Topically
Toxic
The Azoles do what?
Shut down synthesis of ergosterol
Two types of azoles are based on what?
Number of nitrogen atoms in azole ring
Two types of azoles are what?
- Imidazoles (2 nitrogens)
2. Triazoles (3 nitrogens)
Azoles target what enzyme?
cytochrome p450 dependent lanosterol 14-alpha-demethylase
What is the most famous allyamine?
Lamisil
Allylamines are used for what?
Broad spectrum against dermatophytes
What is the mechanism of allylamine action?
Inhibit squalene epoxidase that decreases ergosterol and increases squalene
How is allylamine used?
Topically or oral
Echinocandins are what type of molecules?
Lipopeptides
What is mechanism of echinocandins?
Inhibit synthesis of Beta-(1,3)-glucans which are part of cell wall.
Are echinocandins static or cidal?
Either or depending on fungus
Main side effect of echinocandins?
GI upset
What does flucytosine disrupt?
Nucleic acid synthesis?
Structure of flucytosine?
Fluorinated pyrimidine analogue.
What does flucytosine become in the cell?
Which allows it do what?
5-FU and
competes with uracil in RNA
What makes flucytosine special?
Water soluble and gives high concentrationsin CSF, serum and fluids
Is flucytosine used alone mainly?
No, because of secondary resistance
Griseofulvin acts on what fungi?
Dermatophytes
Mechanism of griseofulvin action?
Interferes with microtubules in the nucleus causing inhibition of mitosis
What are the resistance mechanisms to antifungals?
- Changes in target
- loss of permeability
- efflux pumps
