MMI 133

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mct
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195551
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MMI 133
Updated:
2013-01-26 23:50:31
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Part One Five
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Lecture 3, last one before quiz 1
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  1. Fungi
    Important as nosocomial (hospital acquired) infections and as opportunistic infections of immunocompromised, few are primary pathogens
  2. Beneficial functions of fungi
    • Decomposition of plant matter
    • edible mushrooms
    • leavening agent for bread, fermentation for beer, wine, etc.
  3. Ergosterol
    • Cells walls of fungi have ergosterol in cell membrane (unlike the cholesterol that we have)
    • Many antifungal drugs affect ergosterol synthesis;
    • Amphotericin B
    • Azoles
    • Nystatin
  4. 3 types of Fungi
    • 1. Moulds
    • 2. Yeasts
    • 3. Dimorphic
  5. Moulds
    Have caenocytic and septate types (divisions between cells, or none)
  6. Yeasts
    • Oval or spherical
    • reproduce by budding (bud eventually breaks off)
    • If buds fail to detach may form pseudohyphae
    • Candida albicans may attach to epithelial cells as a yeast, but invades deeper tissues by means of psuedohyphae
    • Saccharamyces - yeast-ethanol for wine; carbon dioxide for leavening bread dough
    • Yeasts are capable of facultative anaerobic growth, most moulds are aerobic growth only. (important for invasiveness)
    • Some yeasts produce a polysaccharide capsule eg Cryptococcus neaformans
  7. Dimorphic Fungi
    • Two forms of growth, can grow as a mould or a yeast, temperature dependent
    • Dimorphism: pathogenic species grow as moulds at lower temperatures and yeast at body temperatures.
    • eg Histoplasma capsulatum is a yeast in the body at temp <35C is a mould
    • Dimorphic fungi are not infectious from one person to another - the mould form is spread by spores in air
  8. Sporothrix
    • Also called "Rose Gardener's Disease"
    • Fungal spores introduced into wound
    • Lymphangitis common (usually are or leg) - causes more ulcers as disease progresses
  9. Fungal Reproduction
    • Fungal spores are for reproduction (not survival)
    • Spores are important for identification
    • Fungal spores are very different from bacterial spores
  10. Fungal Nutrition
    • Less nutritionally demanding than bacteria
    • Grow better than bacteria in extreme conditions
    • Most are aerobic
    • Most grow best at 25-30C
  11. Fungal Diseases
    • All fungal diseases are called: mycoses
    • Singular: mycosis
    • 3 types of mycoses: 1 Superficial, 2 Cutaneous, 3 Systemic (3 is more severe, 1 least severe)
  12. Superficial Mycoses
    • fungal infection along surface of hair shafts and outer layer of skin
    • mild infections
    • -black and white piedra (hairs of scalp)
    • -Malassezia furfur (a yeast)
  13. Cutaneous mycoses
    • fungal infection of deeper layers of the epidermis by moulds (eg. athletes foot or ringworm)
    • caused by dermatophytes (degrade keratin)
    • -few different moulds, same mechanism of pathogenicity
    • clinical diseases are called "tineas" (eg. tinea capitis involves head; tinea pedis feet; tinea cruris groin; tinea corporis torso; tinea barbae beard; etc)
  14. Systemic Mycoses
    • Infections in deep tissues (organs)
    • -either caused by primary pathogens such as Histoplasma capsulatum, Coccidioides immitis, Penicillium marneffei
    • -or opportunistic pathogens such as Canadida albicans
  15. Opportunistic fungal pathogens
    • Common cause of infections in immunocompromised individuals (eg. Aspergilosis; caused by Aspergillus niger; infects people with debilitating lunch diseases,
    • immunocompromised
  16. Candidiasis
    • *Canadida albicans
    • causes vulvo-vaginal candidiasis and thrush (occurs in newborns, immunocompromised and in people who have been treated with "broad spectrum" anitibiotics
    • *Normal flora in gut and mouth
  17. 3 types of parasites
    • Protozoa - one-celled eukaryotes
    • Metazoa or Helminths - multicellular eukaryotes
    • Ectoparasites
  18. Protozoa
    • Most reproduce asexually by fission, budding or schizogony (multiple divisions of nucleus and cell)
    • Some reproduce sexually and have gametes (haploid sex cells) eg. Plasmodium species
    • Some have cyst form, protection from inhospitable environments - growing form called "trophozoite"
    • Cyst form may also be called an oocyst in some types of protozoa. e.g. Cryptosporidium species
  19. 9 Protozoans to Know
    • 1. Entamoeba histolytica
    • 2. Giardia lamblia
    • 3. Trichomonas vaginalis
    • 4. Acanthamoeba
    • 5. Cryptosporidium
    • 6. Toxoplasma gondii
    • 7. Trypanosoma
    • 8. Leishmania
    • 9. Plasmodium

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