Summary
Summary of the part Mycology
- Course
- Institution
This is a summary of the part Mycology givn by prof. Louis Maes, of the course Human Parasites, mciro-organisms and zoonoses.
[Show more]
Seller
Followjokestynen
Content preview
HUMAN PARASITES: PARTMYCOLOGY
GENERAL INTRODUCTION
GENERAL CHARACTERISTICS OF TRUE FUNGI (EUMYCOTA)
Antifungals focus on mostly on 2 aspects that are specific for fungi
Cytoplasmic membrane contains sterol:
o Ergosterol is present VS humans which have cholesterol
Cell membrane = outer membrane: chitin, glucan, mannan
All fungi are eukaryotic
Most are filamentous: filaments = hyphae, these exhibit apical growth and form a network of
hyphae called a mycelium
Some are unicellular: e.g. yeasts
Protoplasm of a cell or a hyphae is surrounded by a rigid wall
Many reproduce both sexually and asexually: they both result in the production of spores
Their nuclei are typically haploid and hyphal compartments are often multinucleate
All are chemoheterotrophic (chemo-organotrophic): use carbon from the environment as
energy
They may be free-living or parasitic or mutualistic (symbiotic)
GENERAL STRUCTURE
OF FUNGI
Vegetative hyphae: feeding
o These are present IN the agar
o Can be segmented or non-
segmented
Aerial hyphae: reproduction
Mycellium = large mass of hyphae
Fungael thallus (“body”) consists of hyphae
OF THE YEASTS
1
, Daughter cell will be same size as parent cell
Unicellular: oval to round
Fission yeasts divide symmetrically
Budding yeasts divide asymmetrically (e.g. Candida)
o Bud = knob = blastospore
o Parent cel budding breaks of parent cell ‘scar’ on parent cell
Real hyphen= 1 structure >< pseudohyphen= no full separation (of the knob)
OF DIMORPHIC FUNGI
Can grow both as fungus or as yeast
Dependent on environmental factors: T°, CO2 and nutrients
o E.g. thermal dismorphism: Dimorphism in pathogenic fungi:
37°C → yeast pathogenic form
25°C → fungus
SUBCELLULAR STRUCTURE
Capsule (polysaccharides) in some fungi!! (E.g. Cyptococcus neoformans)
o Protection against phagocytosis (because polysaccharides aren’t recognized)
virulence factor
Also a cell wall and cell membrane
Cytoplasm
o Nucleus & nuclear membrane
o Endoplasmic reticulum
o Mitochondria
o Vacuoles
Cholestrol (present in humans) is replaced by ergosterol (kind of specificity)
o Squalene produce ergosterol
Therapeutic targets for antifungals
o Squalene
o Ergosterol!! (mostly this one)
o Chitin
o Glucan
o DNA/RNA synthesis
Type and relative composition of chitin and glucan are
dependent on the fungal species
o Antifungals focussing on glucan and chitin
have different effects on different fungal species and the susceptibility between the
species can vary
LIFE CYCLE (DON’T NEED TO KNOW THIS)
Assexual
o Filamentous fungi: asexual by fragmentation of hyphae
o Asexual spores: Conidiospore (Aspergilus spp), Chlamydiaspore (C. albicans), Sporangiospore,
Macro-µnidia
2
, o There are conidia + conidiophore spores/conidia are released spores/conidia germinate
Sexual
o Sexual spores: formed by fusion of nuclei of different haploid gametes
o + / - nucleus come together = karyogamy 2n diploid
ISOLATIONoOF Haploid
FUNGI+ mitosis
Nutrients broths and agar’s (with addition of antibiotics (with no antifungal potential) to prevent
bacterial overgrowth)
General: supports the growth of most fungi
o Sabouraud
o Potato Dextrose Agar (PDA): good for growing spores
Selective: permits growth of a particular species
o Nickerson agar (bismuth-sulphate) Candida spp. and other
yeasts
Bismuth-sulphate: some yeast can reduce/metabolize
it colour change
But it’s still quite general: almost all candida
IDENTIFICATION OF FUNGI
Morphological not used a lot: there are other methods
STAINING METHODS
KOH + lactophenol-blue staining
o Function of KOH: clears the sample, it solubilizes, makes it
translucent
o Done correctly immediate diagnosis, but difficult interpretation
Gram-staining
o Candida are Gram-pos
o Hyphen are Gram-neg
Calcofluor
o Fluorescent dyes that bind specifically to the cell wall (to membrane
components)
o Fluorescence microscopic reading!
BIOCHEMICAL
API Candida
o Principle: Enzyme reaction of candida to different
carbohydrates (substrates)
This gives different colors depending on which
carbohydrates are fermented depends on the species
o OPM: Fungi grow slower than bacteria
ChomAgar
o Immediate identification and quantification used a lot in labs
o Agar plate + substrate
3
, o Depending on species (enzymatic digestion of substrate ) different colors (e.g.: C.
albicans = green)
o Advantages: quantitative, different species
o Disadvantage: expensive
ANTIFUNGAL DRUGS
Fungal treatment is always long term!!
TARGETS
Echinocandins, nikkomycin Z: Inhibition of fungal cell wall formation
Sordarins: Interference with protein assembly
Azoles, Polyenes, Terbinafine: Disruption of fungal cell membrane
Flucytosine: Interference with DNA synthesis
TIMELINES FOR SYSTEMIC ANTIFUNGALS
Antifungal treatment is relatively recent
Antifungals are used a lot in the food/agriculture industry
o Other methodsd to preserve food: irradiation (it’s a bit
expensive)
Azoles: o.a. Miconazole (=generic name = active compound)
Amphotericin: works against Leishmania, it’s toxic they make
liposomal formulations: these do cell targeting and integrate into
the cell wall
What to know:
POLYENES 1. Mechanism of action
2. Spectrum
Structures 3. Action: killing, inhibiting multiplication + growth
o High molecular lactones
o Amphophilic compounds: has a lipophilic and ionic part can solubilize to some
extent in water and is highly lipophilic as well
o MW above 500 (oral) absorption is a problem combination of systemic (oral
absorption or IV) and topical (ointments)
Action mechanism
4
The benefits of buying summaries with Stuvia:
Guaranteed quality through customer reviews
Stuvia customers have reviewed more than 700,000 summaries. This how you know that you are buying the best documents.
Quick and easy check-out
You can quickly pay through credit card or Stuvia-credit for the summaries. There is no membership needed.
Focus on what matters
Your fellow students write the study notes themselves, which is why the documents are always reliable and up-to-date. This ensures you quickly get to the core!
Frequently asked questions
What do I get when I buy this document?
You get a PDF, available immediately after your purchase. The purchased document is accessible anytime, anywhere and indefinitely through your profile.
Satisfaction guarantee: how does it work?
Our satisfaction guarantee ensures that you always find a study document that suits you well. You fill out a form, and our customer service team takes care of the rest.
Who am I buying these notes from?
Stuvia is a marketplace, so you are not buying this document from us, but from seller jokestynen. Stuvia facilitates payment to the seller.
Will I be stuck with a subscription?
No, you only buy these notes for $3.23. You're not tied to anything after your purchase.
Can Stuvia be trusted?
4.6 stars on Google & Trustpilot (+1000 reviews)
56326 documents were sold in the last 30 days
Founded in 2010, the go-to place to buy study notes for 14 years now