Card Set Information

2013-12-02 11:29:44
Fungi TUSPMMicroExam4
Vlahovic Micro Exam 4
Show Answers:

  1. What is the essential sterol in fungi?
  2. What class are fungi?
    • •eukaryotic
    • most are strict aerobes
    • NO strict anaerobes
  3. 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*)
  4. What DONT fungal cell walls have?
    • muramic acid
    • teichoic acids
    • peptidoglycan
  5. What DO fungal cell walls possess?
    • Hexos and hexosamine polymers
    • CHITIN
    • glucans
    • mannans
  6. What is chitin?
    composed of gluocosamine subunits (linked like cellulose)
  7. 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
  8. Heterophilic metabolism: what do fungi require as an energy source?
    organic compounds
  9. Where di saprophytis derive nutrients from?
    decaying oraganic material-- will grow on simple carbon source nitrate ions as a nitrogen source
  10. 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
  11. What is the morphology of yeast?
    - smooth colonies like   bacteria;  microscopically -  single cells which bud
  12. 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
  13. What does dimorphism mean? in regards to fungi?
    • Fungi can grow as yeast or mold
    • Some fungi can grow as either phase
  14. What does dimorphism depend on?
    Environmental factors
  15. 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

    Name some features
    • Dimorphic fungi
    • grow as budding yeast cells
    • filamentous hyphae (bottom of picture)
    • intermediate forms
    • *most important fungi
  17. Do most Fungi have a sexual spore phase?
  18. How is a sexual spore produced?
    fusion of 2 nuclei that general undergo mitosis
  19. Is sexual mating necessary for continuation of the fungal species?
    • NO.
    • asexual spores continus to maintain and disseminate these species
  20. Conidia
    • = reproductive elements producers by:
    • -budding off of conidiogenous hypae
    • - differentiation of preformed hypae
  21. Spores
    • = reproductive elements produced by:
    • -consecutive cleavages of a sporangium
    • -major method for maintenance and dissemination of many fungi*
  22. Blastoconidia
    formation of a bud in yeasts
  23. Mold growth
    produce separate or non separate hyphae which extend to from a mycelium
  24. Hyphae
    • branching tubular structures that make up the mycelium
    • septae divide the hyphae into compartments (not cells)
  25. Conencocytic hyphae (non-septate)
    • considered more primitive.
    • when hyphal strand is damaged, entires strand dies!
  26. Septate hyphae
    • pores between adjacent compartments can be plugged preventing death of entire strand
  27. fungal taxonomy
    based on sexual spores and septation
  28. Zygomycetes
    • gametes and asexual reproduction with the formation of zygospores
    • Aspetate
    • Asexaul spore: Sporangiospore
  29. Ascomycetes
    • ascus with the production of ascospores
    • Septate
    • Asexaul spore: Conidia
  30. Basidiomycetes
    • basidium with the production of basidospores
    • Septate
    • Asexaul spore: Conidia
  31. Deuteromycetes
    (Fungi Imperfecti)
    • no recognizable form of sexual reproduction
    • Asexaul spore: Conidia
    • Septate
  32. zygomycetes examples
    • Mucor
    • Rhizoporus
  33. Ascomycetes examples
    • -Blastomyces
    • -Dermatophytes
    • -Histoplasma capsulatum
    • -Candida
    • -Aspergillus
  34. Basidiomycetes examples
    Crytococcus neoformans
  35. Deuteromycetes examples
  36. Dermatophytes: 
    tissues/ diseases
    • Superficial skin fungi
    • indolent lesions of the skin and its appendages
    • Ex: ring worm, athlete's feet
  37. What are the most virulent fungi?
    • systematic pathogens
    • can caused serious progressive disease in previously healthy people
  38. 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
  39. Virulence factors
    • adherence
    • invasion
    • extracellular enzymes
    • phagocytic interactions
    • tissue injury
    • immmunity
  40. adherence of fungi
    • Some yeasts can colonize mucosa of GI/UG
    • require surface adhesion on the microbe and a receipt on the epi cell
  41. invasion of fungi
    • across surface barrier.
    • may be though mechanical breaks in epithelium
  42. Ex of invasion of fungi
    C. albicans-- form hyphae and pseudohyphae that allow penetration and spread (mechanism unknown)
  43. EXC enzymes of fungi
    • proteases
    • elastases
  44. Phagocytic interactions of fungi
    - neutrophils and macrophages are able to kill hyphae of most fungi

    -dimorphic species are more resistant to killing by neutrophils
  45. 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
  46. 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
  47. 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.
  48. 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
  49. HUmoral immunity of fungi
    -opsonizing antibody effective in some yeast infections
  50. 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
  51. Cellular immunity fo fungi
    • systematic disease associated with deficiencies in neutrophils and T-cell mediated immunity
    • fungi that escapee neutrophils grow slowly in macrophages
  52. 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
  53. 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
  54. Why is SDA not the best growth medium for fungi?
  55. Isolate fungi from clinical specimens? Use what agar?
    SDA with chloramphenicol
  56. Mycosel (Mycobiotic) agar
    ◦ isolate clinical fungal specimens

    • ◦ same as SDA but with chlormephenicol actidione
    • (cycloheximide)

    ◦ @ pH 6.8
  57. 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
  58. Brain Heart Infusion agar
    • nutrient enriched
    • primary to grow yeast cultures especially with dimorphic fungi
  59. Potato Dextrose Agar
    deficient medium used to stimulate sporulation of many fungi
  60. Corn Meal Agar
    most commonly used to induce condition of fungi that do not produce sufficient spores on SDA, DTM, or Mycosel
  61. KOH preparation
    • Mold ID
    • microscopic characteristic of fungi
    • direct microscopic examination of skin scrapings
  62. LPCB mount
    • Mold ID 
    • lactophenol cotton blue 
    • miscroscopic examination of cultures
  63. Yeasts ID
    ID by sugar fermentation, sugar assimilation and some biochemical patterns
  64. 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
  65. KOH is useful to see...?
  66. What does a PAS tell you?
    • fungus
    • inflammation
  67. methenamine silver
    stain all fungi and are very helpful for detection of fungi in tissue sections
  68. Fungi Elicit 3 Types of Conditions in Humans
    • 1. Allergy - IgE - mold allergy Non-complicated Type I
    • 2. Toxins - Aflatoxins
    • 3. Disease - mycosis