8

• how fungi is classified

  yeasts, mould (septate and mucorales) and dimorphic fungi
• yeast example 


  Candida spp
• mucorales example


  Rhizopus spp
• septate mould example


  aspergillus spp
• dimorphic fungi 


  moulds at room temp, yeast at 37 degrees are uncommon infections, slow and hard to treat
• yeast 


  microscopic single cell organism, round, reproduce by budding off bit of cytoplasm (mitosis)
• sepate moulds


  multicellular organism, divisions in fungal structure (septa) and hyphae are common moulds that produce spores
• mucorales


  multicellular organism is aseptate (no division, not broken up into individual cells) with no hyphae. rare cause of human infections
• most common serious fungal infections

  HIV/AIDs, TB and TB like infections, cancer and fungal infections, eye infections
• who is at risk of eye infections (fungal keratitis)

  live in tropical climates, trauma to eye
• who is at risk of TB fungal infection

  those who have had TB recently , part of lung tissue destroyed helps aspergillus group
• why is it hard to make anti fungals

  fungi are eukaryotes so many similar processes to humans
• 3 different features of fungal cells wall

  cell membrane contains ergosterol not cholesterol, polysaccharides mannan, glucan, chitin (instead of teichonic acid, lipopolysaccharides, peptidoglycan)
• anti fungal drug inhibit NA synthesis example

  fluorocytosine
• anti fungal drug inhibit ergosterol biosynthesis example

  azoles
• anti fungal drug inhibit glucan synthesis pathway

  echinocandins (disrupt cell wall structure)
• antifungal drug binds with ergosterol and disrupt membrane integrity

  polyenes
• most common used anti fungal drug

  azoles
• 4 types anti fungal drugs

  1. inhibit NA synthesis (last resort, similar)
  2. inhibit ergosterol biosynthesis
• 4 types anti fungal drugs

  1 - inhibit NA synthesis (last resort, toxic) 2 - inhibit ergosterol synthesis 3 - inhibit glucan biosynthesis 4 - bind ergosterol and disrupt membrane integrity
• 5 types of fungal infections

  invasive, chronic or deep tissue, mucosal, skin/hair/nail, allergic
• invasive fungal infections 


  only really in immune deficient patients, rapidly progressing and often fatal
• invase fungal infection example

  cryptococcal meningitis cause by an encapsulated yeast causing subacute meningitis
• chronic or deep tissue fungal infections

  some fungal infections difficult to treat leading to long term infection, local trauma to eye, skin risk factors
• chronic or deep tissue example

  fungal keratitis (corneal ulcer), caused by aspergillum after ocular injury fungal spores implant on transparent cornea causing inflammation
• mucosal fungal infection


  effect mucus membranes of vagina, oesophagus, mouth caused by candida albicans forming white plaque on mucosa
• mucosal fungal infection example

  thrush - candida albicans in mouth or vagina forming plaque, often recurrent as is a commensal (overgrowth with changing immune status)
• skin/nail/hair fungal infections


  most common type, human-human transmission of fungi, occurs in healthy people, able to survive on skin
• skin/hair/nail fungal infection example

  athletes foot, between toes cracking with painful fissure can occur to anyone with dampness between toes
• moccasin type athletes foot 


  most serious, whole foot infected with eczema reaction and fissuring of heel
• allergic fungal infection


  upper/lower respiratory tract, affected people have allergies to fungi and genetically predisposed
• allergic fungal infection symptoms

  mucus production, mucosal swelling in airways, nose and sinuses
• allergic fungal infection example


  allergic bronchopulmonary aspergillosis
• how allergic bronchopulmonary aspergillosis is caused

  inhale aspergillus conidia, becomes trapped in airway mucosa, spores germinate and form hyphae in bronchi = stimulus allergic inflammatory response (genetically predisposed people)
• how aspergillus conidia spores cause allergic response

  exaggerated Th2 response (Th1/2 imbalance) giving maladaptive immune response, promotes airway inflammation and recruits mast cells, IgE production, eosinophils = airway narrowing, mucus plug, lung tissue breakdown