|
Home > Preview
The flashcards below were created by user
xbecx10
on FreezingBlue Flashcards.
-
What is the essential sterol in fungi?
ergosterol
-
What class are fungi?
- •eukaryotic
- most are strict aerobes
- NO strict anaerobes
-
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*)
-
What DONT fungal cell walls have?
- muramic acid
- teichoic acids
- peptidoglycan
-
What DO fungal cell walls possess?
- Hexos and hexosamine polymers
- CHITIN
- glucans
- mannans
-
What is chitin?
composed of gluocosamine subunits (linked like cellulose)
-
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
-
Heterophilic metabolism: what do fungi require as an energy source?
organic compounds
-
Where di saprophytis derive nutrients from?
decaying oraganic material-- will grow on simple carbon source nitrate ions as a nitrogen source
-
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
-
What is the morphology of yeast?
- smooth colonies like bacteria; microscopically - single cells which bud
-
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
-
What does dimorphism mean? in regards to fungi?
- Fungi can grow as yeast or mold
- Some fungi can grow as either phase
-
What does dimorphism depend on?
Environmental factors
-
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
-
This is CANDIDA ALBICANS:
Name some features
- Dimorphic fungi
- grow as budding yeast cells
- filamentous hyphae (bottom of picture)
- intermediate forms
- *most important fungi
-
Do most Fungi have a sexual spore phase?
NO
-
How is a sexual spore produced?
fusion of 2 nuclei that general undergo mitosis
-
Is sexual mating necessary for continuation of the fungal species?
- NO.
- asexual spores continus to maintain and disseminate these species
-
Conidia
- = reproductive elements producers by:
- -budding off of conidiogenous hypae
- - differentiation of preformed hypae
-
Spores
- = reproductive elements produced by:
- -consecutive cleavages of a sporangium
- -major method for maintenance and dissemination of many fungi*
-
Blastoconidia
formation of a bud in yeasts
-
Mold growth
produce separate or non separate hyphae which extend to from a mycelium
-
Hyphae
- branching tubular structures that make up the mycelium
- septae divide the hyphae into compartments (not cells)
-
Conencocytic hyphae (non-septate)
- considered more primitive.
- when hyphal strand is damaged, entires strand dies!
-
Septate hyphae
- pores between adjacent compartments can be plugged preventing death of entire strand
-
fungal taxonomy
based on sexual spores and septation
-
Zygomycetes
- gametes and asexual reproduction with the formation of zygospores
- Aspetate
-
Ascomycetes
- ascus with the production of ascospores
- Septate
- Asexaul spore: Conidia
-
Basidiomycetes
- basidium with the production of basidospores
- Septate
- Asexaul spore: Conidia
-
Deuteromycetes
(Fungi Imperfecti)
- no recognizable form of sexual reproduction
- Septate
-
-
Ascomycetes examples
- -Blastomyces
- -Dermatophytes
- -Histoplasma capsulatum
- -Candida
- -Aspergillus
-
Basidiomycetes examples
Crytococcus neoformans
-
Deuteromycetes examples
Fusarium
-
Dermatophytes:
tissues/ diseases
- Superficial skin fungi
- indolent lesions of the skin and its appendages
- Ex: ring worm, athlete's feet
-
What are the most virulent fungi?
- systematic pathogens
- can caused serious progressive disease in previously healthy people
-
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
-
Virulence factors
- adherence
- invasion
- extracellular enzymes
- phagocytic interactions
- tissue injury
- immmunity
-
adherence of fungi
- Some yeasts can colonize mucosa of GI/UG
- require surface adhesion on the microbe and a receipt on the epi cell
-
invasion of fungi
- across surface barrier.
- may be though mechanical breaks in epithelium
-
Ex of invasion of fungi
C. albicans-- form hyphae and pseudohyphae that allow penetration and spread (mechanism unknown)
-
-
Phagocytic interactions of fungi
- neutrophils and macrophages are able to kill hyphae of most fungi
-dimorphic species are more resistant to killing by neutrophils
-
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
-
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
-
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.
-
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
-
HUmoral immunity of fungi
-opsonizing antibody effective in some yeast infections
-
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
-
Cellular immunity fo fungi
- systematic disease associated with deficiencies in neutrophils and T-cell mediated immunity
- fungi that escapee neutrophils grow slowly in macrophages
-
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
-
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
-
Why is SDA not the best growth medium for fungi?
SUPPRESSES conidiation PROMOTES MYCELIAL GROWTH
-
Isolate fungi from clinical specimens? Use what agar?
SDA with chloramphenicol
-
Mycosel (Mycobiotic) agar
◦ isolate clinical fungal specimens
- ◦ same as SDA but with chlormephenicol actidione
- (cycloheximide)
◦ @ pH 6.8
-
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
-
Brain Heart Infusion agar
- nutrient enriched
- primary to grow yeast cultures especially with dimorphic fungi
-
Potato Dextrose Agar
deficient medium used to stimulate sporulation of many fungi
-
Corn Meal Agar
most commonly used to induce condition of fungi that do not produce sufficient spores on SDA, DTM, or Mycosel
-
KOH preparation
- Mold ID
- microscopic characteristic of fungi
- direct microscopic examination of skin scrapings
-
LPCB mount
- Mold ID
- lactophenol cotton blue
- miscroscopic examination of cultures
-
Yeasts ID
ID by sugar fermentation, sugar assimilation and some biochemical patterns
-
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
-
KOH is useful to see...?
hyphae
-
What does a PAS tell you?
-
methenamine silver
stain all fungi and are very helpful for detection of fungi in tissue sections
-
Fungi Elicit 3 Types of Conditions in Humans
- 1. Allergy - IgE - mold allergy Non-complicated Type I
- 2. Toxins - Aflatoxins
- 3. Disease - mycosis
|
|
Get the free mobile app
Take the Quiz
Learn more
Learn more