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Lecture notes

Fungi

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Pathogenic fungi

         Fungi include yeast and mould

         most are harmless, 50 species cause human diseases

         incidence of serious fungal infection low

         certain superficial fungal infection more common

 

Fungal Disease Mechanisms;

 

  1. Some fungi cause immune reponse - may result in allergic ( hypersensitivity) reaction upon exposure to specific fungal antigen- eg. Aspergillus cause asthma & other allergic reaction
  2. Production and action of mycotoxin (fungal exotoxin) eg. Aspergillus flavus grow on stored grains- aflatoxins highly toxic, induce tumors in some animals feeding on contaminated grains
  3. Infection- growth of fungus on/in body + mycoses- range in severity - innocuous, superficial to life-threatening disease

 

Mycoses

 

3 categories:

I) Superficial Mycoses

          colonisation of skin, hair/nails, infect only surface layers

         disease is benign & self-limiting eg. Athlete’s foot (Tricophyton)

         spread-personal contact with infected person, contaminated surfaces-bathtub, towels/bed linen

         Treatment: topical application miconazole or griseofulvin

         sometimes orally-drug enter bloodstream pass to skin inhibiting fungal growth

 

II) Subcutaneous Mycoses

         involve deeper layers of skin

         disease sporotrichosis - starts with infection of small wounds/abrasions forms ulcer and chancres

         Treatment: oral potassium iodide or oral ketoconazole

 

III) Systemic Mycoses

         fungal growth in internal organs -

classified as primary and secondary infections

-Primary- resulting in healthy individual due to fungal infection

-Secondary- due to individual who has impaired immunity - antibiotic therapy/immunosuppression

 

         Histoplasmosis (Histoplasma capsulatum) and coccidiomycosis(Coccidioides immitis)both soil organisms, common & widespread  diseases in US.

         Infection-airborne spores germinate an grow in lungs-respiratory disease

         opportunistic fungal infection cauisng serious infections in individual with impaired immunity eg.AIDS patients

         Effective fungal diseases difficult - lack of suitable fungus-specific antibiotic, most of these antibiotics also harm other eukaryotic organisms including human host

         amphotericin B most effective, treatment of systemic infection inhuman- side effects kidney toxicity

         elimination lf fungal pathogens from environment impractical-limitless reservoir

         decontamination and air filteration in restricted environment possible

 

 

 

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