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What is a fungus?

  • A chemo-organotrophic eukaryote that lacks chlorophyll and forms spores. 
  • Its cell wall contains polysaccharides, often chitin or glucan, and it absorbs nutrients. 
  • Its membrane contains ergosterol as the major sterol. 
  • Classification is principally based on morphology.
  • Informally we refer to the major types as moulds, yeasts or mushrooms



  • Fungi that favour a unicellular habit


The fungal kingdom

  • Fungi from all 3 groups can cause disease in humans
  • Mycytes



Moulds with a tendancy to degrade keratin (protein that protects epithelial cells from damage or stress) as a nutrient source.

Causative agents ►:Epidermophyton, Microsporum and Trichophyton spp.


Fungi are a significant cause of non-fatal diseases

Athlete’s foot: caused by Epidermophyton, Microsporum and Trichophyton spp.

Thrush: caused by Candida spp.

Pityriasis versicolor: caused by Malassezia spp.


Fungal infections 


 Acting as opportunistic pathogens of immunocompromised patients such as:

  • Candida species 
  • Aspergillus spp


Candida species

  • Infect deep organs of patients with various types of immune dysfunction, e.g. after abdominal surgery, burns, etc


Aspergillus spp

Infect deep organs of patients undergoing chemotherapy, stem cell transplantation


Describe the host factors that contribute to the pathogenicity of fungal infections?

  • Favourable micro-environments encourage growth of fungi on skin and mucous membranes
  • Broad-spectrum antibacterial agents reduce competition for epithelial colonization sites in the gut
  • Immunosuppression of all types may create a window of opportunity for fungal invasion



Candida and candidiasis

  • Worldwide distribution.  Candida species commensal to GI tract, some are environmental. Most infections are endogenous.
  • Candida spp. are yeasts



Candida infection

Superficial: mouth, vagina, penis, skin, nails

Deep-seated:disseminated infections in immunocompromised hosts(abdominal surgery, major burns, etc.)




  • Aspergillus spp. are moulds
  • They are ubiquitous in the environment: infection occurs by inhalation of conidia
  • These fungi are strongly angioinvasive (penetrate the walls of blood vessels)




  Describe the diagnostic methods for detecting fungi?►

  • Direct detection such as histopatholgy  (tissue examination) and high resolution CT-scan.
  • Direct smear
  • Detection of circulating fungal antigens
  • Detection of circulating antibodies to  fungi
  • PCR for fungal DNA
  • Culture of fungus from normally sterile site