Fungi Flashcards
What are the host factors that contribute to the growth of fungal infections?
Warm, moist environments (e.g. skin and mucous membranes)
Antibiotic use decreases the competition for epithelial colonization sites in the gut.
Immunosuppression gives an opportunity for fungal invasion with a reduced risk of an immune response.
What are the different types of immunosuppression?
Iatrogenic-immunosuppression due to treatment, e.g. chemotherapy, steroids or after organ transplants
Diseases that suppress the immune system, e.g. AIDs, Leukaemia
What are the methods of detecting fungi?
Direct detection by:
- histopathology
- High-resolution CT scan
- Smear test
Other detection methods: >fungal antigen detection >antibody detection >PCR of fungal DNA >culture of fungus from a normally sterile site
Name the types of stain that can be used and what they show
Periodic Acid Shiff (PAS) stain- glycoproteins
Calcofluor White Stain- binds to cellulose and chitin, in the fungal cell wall
What is ChromAgar Candida?
It is a selective medium on which Candida species can be grow. The different Candida species present can be identified due to the different colours the part of agar they are on has. The colour changes are due to a change in pH.
What is a complement fixation test?
It is an immunological test used to detect specific antigens or antibodies in serum.
When are complement fixation tests used?
To detect microorganisms (identify infection type) that are difficult to culture.
What do polyenes do?
They bind to ergosterol to form polyene-ergosterol complexes which increase cell wall permeability (they are a type of anti-fungal)
What is the problem with using polyenes? How can they be administered?
They bind to cholesterol as well, which is in human cell membrane and are therefore toxic.
IV, suspension, orally, topically
What do azoles do?
They inhibit ergosterol synthesis, which causes toxic sterols to be produced. can be administered by IV, topically or orally.
What has to be monitored when allymines are used?
Liver function
How do echinocandins work and how are they administered?
Inhibit the synthesis of the polysaccharide, glucan
They are given by IV to treat Candida or aspergillus infections.
