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What is the essential sterol in fungi?
ergosterol
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What class are fungi?
- •eukaryotic
- most are strict aerobes
- NO strict anaerobes
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Describe a Fungal cell
- •They possess at least one nucleus
- surrounded by a nuclear membrane
•Have chromosomes
•Have cytoplasmic organelles
•Cell membrane contains sterols (ergosterol*)
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What DONT fungal cell walls have?
- muramic acid
- teichoic acids
- peptidoglycan
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What DO fungal cell walls possess?
- Hexos and hexosamine polymers
- CHITIN
- glucans
- mannans
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What is chitin?
composed of gluocosamine subunits (linked like cellulose)
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Describe the Fungal cell memebrane
- Bilayered
- –Contains phosphatidylethanolamine
- (phospholipid) and phosphatidylcoline
- –Ergosterol and zymosterol – major sterols
- –Cholesterol is usually absent
- Functions as an osmotic barrier.
- Facilitates synthesis of cell wall material
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Heterophilic metabolism: what do fungi require as an energy source?
organic compounds
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Where di saprophytis derive nutrients from?
decaying oraganic material-- will grow on simple carbon source nitrate ions as a nitrogen source
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How does heterophilic metabolism occur?
- - absorptive mode of nutrition - secrete digesting enzymes into environment - simpler
- substances from digested macromolecules enter cell by osmosis or specialized transport systems
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What is the morphology of yeast?
- smooth colonies like bacteria; microscopically - single cells which bud
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Describe Molds
- fuzzy colonies microscopically how the cell to extend by formation of tube-like extensions with thinck parallel walls called HYPEA
- Separate or non separate
- A mass of hypea= mycelium
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What does dimorphism mean? in regards to fungi?
- Fungi can grow as yeast or mold
- Some fungi can grow as either phase
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What does dimorphism depend on?
Environmental factors
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What is the difference between mold and yeast in regards to their location/temperature?
- Yeast-- usually found WITHIN a system so can live inside a body
- Mold form-- room temperature
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This is CANDIDA ALBICANS:

Name some features
- Dimorphic fungi
- grow as budding yeast cells
- filamentous hyphae (bottom of picture)
- intermediate forms
- *most important fungi
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Do most Fungi have a sexual spore phase?
NO
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How is a sexual spore produced?
fusion of 2 nuclei that general undergo mitosis
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Is sexual mating necessary for continuation of the fungal species?
- NO.
- asexual spores continus to maintain and disseminate these species
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Conidia
- = reproductive elements producers by:
- -budding off of conidiogenous hypae
- - differentiation of preformed hypae
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Spores
- = reproductive elements produced by:
- -consecutive cleavages of a sporangium
- -major method for maintenance and dissemination of many fungi*
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Blastoconidia
formation of a bud in yeasts
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Mold growth
produce separate or non separate hyphae which extend to from a mycelium
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Hyphae
- branching tubular structures that make up the mycelium
- septae divide the hyphae into compartments (not cells)
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Conencocytic hyphae (non-septate)
- considered more primitive.
- when hyphal strand is damaged, entires strand dies!

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Septate hyphae
- pores between adjacent compartments can be plugged preventing death of entire strand

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fungal taxonomy
based on sexual spores and septation
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Zygomycetes
- gametes and asexual reproduction with the formation of zygospores
- Aspetate
Asexaul spore: Sporangiospore
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Ascomycetes
- ascus with the production of ascospores
- Septate
- Asexaul spore: Conidia
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Basidiomycetes
- basidium with the production of basidospores
- Septate
- Asexaul spore: Conidia
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Deuteromycetes
(Fungi Imperfecti)
- no recognizable form of sexual reproduction
Asexaul spore: Conidia - Septate
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Ascomycetes examples
- -Blastomyces
- -Dermatophytes
- -Histoplasma capsulatum
- -Candida
- -Aspergillus
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Basidiomycetes examples
Crytococcus neoformans
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Deuteromycetes examples
Fusarium
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Dermatophytes:
tissues/ diseases
- Superficial skin fungi
- indolent lesions of the skin and its appendages
- Ex: ring worm, athlete's feet
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What are the most virulent fungi?
- systematic pathogens
- can caused serious progressive disease in previously healthy people
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Pathenogensis of fungi
- most are oppurtunistic
- 1000/s of aerosol conidia and spores inhaled daily
- some are normal flora
- systematic infections= uncommon
- progressive systematic fungi infections= most difficult to diagnosis and therapeutic problems in infectious disease (esp in immunocompromised)
- spores/components= could be allergen. sting hypersensitivity rxn does not require growth or viability of the fungus
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Virulence factors
- adherence
- invasion
- extracellular enzymes
- phagocytic interactions
- tissue injury
- immmunity
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adherence of fungi
- Some yeasts can colonize mucosa of GI/UG
- require surface adhesion on the microbe and a receipt on the epi cell
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invasion of fungi
- across surface barrier.
- may be though mechanical breaks in epithelium
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Ex of invasion of fungi
C. albicans-- form hyphae and pseudohyphae that allow penetration and spread (mechanism unknown)
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Phagocytic interactions of fungi
- neutrophils and macrophages are able to kill hyphae of most fungi
-dimorphic species are more resistant to killing by neutrophils
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Ex: of dimorphic fungi which are yeasts at one temp and transform to hype at another temp
- C. albicans
- yeast @ 25d C
- hyphae @ 37d C
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Coccidiodes immitis
- contanins component in the call of its conidial (infective phase that is antiphagocytic
- hyphae convert to a spherule phase in tissue and become resistant
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Tissue injury by fungi
- - none of the extracellular products of
- opportunistic fungi have been shown to injure the host directly
- - exotoxins / mycotoxins are produced in the environment by a number of fungi but not in
- vivo
- - injury caused by fungal infections is due to
- the inflammatory and immune responses
- stimulated by the prolonged presence of the fungus.
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Immunity of fungi
- intact immune response prevents infection by fungi and progressive disease
- T-cell mediated response of Primary importance
- progressive fungal diseases occur in immunocompromised patients
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HUmoral immunity of fungi
-opsonizing antibody effective in some yeast infections
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Ex: of humoral immunity of fungi
- Cryptococcus neoformans -antibody controls infection
- enhances killing by phagocytes
- capsule of C. neoformans antiphagocytic - antibody to capsule similar to encapsulated bacterial pathogens
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Cellular immunity fo fungi
- systematic disease associated with deficiencies in neutrophils and T-cell mediated immunity
- fungi that escapee neutrophils grow slowly in macrophages
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Cultivation of Fungi: physiological considerations
- O2: (most= aerobic)
- temp : mesophilic
- Moisture: 75-95% humidity
- pH tolerance: 5-6 optimal
- Generation time: yeasts= 2-3 days. molds= 1-3 WKS
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Sabouraud Dextrose Agar
◦ traditional growth media for fungi
◦ peptone, dextrose at pH 5.6
◦low pH retards growth of many bacteria
- ◦NOT the best medium because it SUPPRESSES
- conidiation and PROMOTES MYCELIAL GROWTH
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Why is SDA not the best growth medium for fungi?
SUPPRESSES conidiation PROMOTES MYCELIAL GROWTH
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Isolate fungi from clinical specimens? Use what agar?
SDA with chloramphenicol
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Mycosel (Mycobiotic) agar
◦ isolate clinical fungal specimens
- ◦ same as SDA but with chlormephenicol actidione
- (cycloheximide)
◦ @ pH 6.8
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Dermatophyte Test Medium (DTM)**
◦ used to isolate dermatophytes from clinical skin and nail specimens
- ◦ contains cycloheximdes, gentamycin, and
- chlortetracycline to suppress common bacteria and non-fermatophilic fungi
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Brain Heart Infusion agar
- nutrient enriched
- primary to grow yeast cultures especially with dimorphic fungi
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Potato Dextrose Agar
deficient medium used to stimulate sporulation of many fungi
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Corn Meal Agar
most commonly used to induce condition of fungi that do not produce sufficient spores on SDA, DTM, or Mycosel
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KOH preparation
- Mold ID
- microscopic characteristic of fungi
- direct microscopic examination of skin scrapings
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LPCB mount
- Mold ID
- lactophenol cotton blue
- miscroscopic examination of cultures
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Yeasts ID
ID by sugar fermentation, sugar assimilation and some biochemical patterns
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Lab diagnosis
- Direct examination of pus, fluid, or tissues
- 10 – 20% KOH
- Heat slide and observe under microscope
- Use 20X or 40X magnification
- Fungi remain intact while tissue cells are disrupted
- Culture - use media containing antibacterial antibiotics
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KOH is useful to see...?
hyphae
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What does a PAS tell you?
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methenamine silver
stain all fungi and are very helpful for detection of fungi in tissue sections
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Fungi Elicit 3 Types of Conditions in Humans
- 1. Allergy - IgE - mold allergy Non-complicated Type I
- 2. Toxins - Aflatoxins
- 3. Disease - mycosis
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