Diagnostics and Antifungals Flashcards
How do you prove mycoses
- microscopy shows fungal elements associated with tissue damage or the fungus itself
- culture shows fungus in normally sterile site
How do you find probable mycoses
- has host factor of immunodeficiency
- clinical evidence such as CT
- mycological evidence such as culture or fungal antigen detection
What do you look for with microscopy?
- stain for chitin
- stain candidiaphores
- reverse stain capsule
- Gram stain - yeast usually G+
- histological staining to see example spherule
What are the disadvantages of microscopy?
- not definitive species ID
- requires tissue or serum or invasive procedures
- not very sesitive
- need large amount of fungi
Whats the advantages of cultures?
- CHROMagar to ID candida species
- show thermal dimorphism
Whats the disadvantages to cultures?
- clinical relevance uncertain (false positives, esp. candida)
- requires sample with viable organism
- long time to grow
How can you use immunological memory to detect mycoses?
- if had previous infection then you have reactive T cells
- T cells produce IFNgamma and IL8 which cause inflammation and a big red spot
How can you use fungal antibodies to test for mycoses?
- separate antigens on gel
- add patient serum
- if light up = infection
ELISA (Enzyme-Linked ImmunoSorbent Assay)
- bind antigen to bottom of tube
- add patient serum
- wash
- add florescent antibody to constant region of patient antibody
- wash
- if light up = infection
Whats the disadvantage of ELISA
antibodies are also evidence of past infections
ELISA/EIA (Enzyme-linked Immuno Assay)
- binds antibody to bottom of tube
- add patient serum
- wash
- add florescent antibody that binds antigen
- wash
- if light up = antigen in patient serum = active infection
What are the advantages to EIA
- detects active infection
- indicative of levels of fungemia
What are the disadvantages to EIA
- low sensitivity (low antigen levels until dissemination)
- preblems with specificity (esp. Histo/Blasto/Cocc because cross reactivity)
How do you detect beta glucan (horseshoe crab version)
- horseshoe crab sacrifice
- their Factor G is activated by beta glucan
- this activates clotting enzymes OR you can use a color changing molecule
How do you detect beta glucan (catheter version)
- beta glucan is shed from biofilm
- can detect beta glucans peripherally from catheter biofilm
How do you detect mycoses with DNA?
- look at ITS1 and ITS2 polymorphisms
- can analyze ITS sizes and also look at point mutations
What are the advatages to using fungal DNA to detect?
- highly specific
- only have fungal DNA if active infection
What are the advatages to using fungal DNA to detect?
- highly specific
- only have fungal DNA if active infection
What are the disadvantages to fungal DNA to detect?
- requires molecular laboratory
- clinical relevance uncertain (normal flora candida for example)
allylamines
inhibit sterol biosynthesis via squalene to lanosterol
azoles (imidazoles and triazoles)
inhibit sterol biosynthesis via lanosterol and 14-demethyllanosterol
polyenes
inhibit ergosterols themselves
How do polyenes kill?
act like AMPs to create pores
How do polyenes kill?
act like AMPs to create pores
