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Eukaryotic Pathogens > Diagnostics and Antifungals > Flashcards

Diagnostics and Antifungals Flashcards

1
Q

How do you prove mycoses

A
  • microscopy shows fungal elements associated with tissue damage or the fungus itself
  • culture shows fungus in normally sterile site
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2
Q

How do you find probable mycoses

A
  • has host factor of immunodeficiency
  • clinical evidence such as CT
  • mycological evidence such as culture or fungal antigen detection
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3
Q

What do you look for with microscopy?

A
  • stain for chitin
  • stain candidiaphores
  • reverse stain capsule
  • Gram stain - yeast usually G+
  • histological staining to see example spherule
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4
Q

What are the disadvantages of microscopy?

A
  • not definitive species ID
  • requires tissue or serum or invasive procedures
  • not very sesitive
  • need large amount of fungi
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5
Q

Whats the advantages of cultures?

A
  • CHROMagar to ID candida species
  • show thermal dimorphism
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6
Q

Whats the disadvantages to cultures?

A
  • clinical relevance uncertain (false positives, esp. candida)
  • requires sample with viable organism
  • long time to grow
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7
Q

How can you use immunological memory to detect mycoses?

A
  • if had previous infection then you have reactive T cells
  • T cells produce IFNgamma and IL8 which cause inflammation and a big red spot
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8
Q

How can you use fungal antibodies to test for mycoses?

A
  • separate antigens on gel
  • add patient serum
  • if light up = infection
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9
Q

ELISA (Enzyme-Linked ImmunoSorbent Assay)

A
  • bind antigen to bottom of tube
  • add patient serum
  • wash
  • add florescent antibody to constant region of patient antibody
  • wash
  • if light up = infection
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10
Q

Whats the disadvantage of ELISA

A

antibodies are also evidence of past infections

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11
Q

ELISA/EIA (Enzyme-linked Immuno Assay)

A
  • 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
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12
Q

What are the advantages to EIA

A
  • detects active infection
  • indicative of levels of fungemia
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13
Q

What are the disadvantages to EIA

A
  • low sensitivity (low antigen levels until dissemination)
  • preblems with specificity (esp. Histo/Blasto/Cocc because cross reactivity)
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14
Q

How do you detect beta glucan (horseshoe crab version)

A
  • horseshoe crab sacrifice
  • their Factor G is activated by beta glucan
  • this activates clotting enzymes OR you can use a color changing molecule
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15
Q

How do you detect beta glucan (catheter version)

A
  • beta glucan is shed from biofilm
  • can detect beta glucans peripherally from catheter biofilm
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16
Q

How do you detect mycoses with DNA?

A
  • look at ITS1 and ITS2 polymorphisms
  • can analyze ITS sizes and also look at point mutations
17
Q

What are the advatages to using fungal DNA to detect?

A
  • highly specific
  • only have fungal DNA if active infection
17
Q

What are the advatages to using fungal DNA to detect?

A
  • highly specific
  • only have fungal DNA if active infection
18
Q

What are the disadvantages to fungal DNA to detect?

A
  • requires molecular laboratory
  • clinical relevance uncertain (normal flora candida for example)
19
Q

allylamines

A

inhibit sterol biosynthesis via squalene to lanosterol

20
Q

azoles (imidazoles and triazoles)

A

inhibit sterol biosynthesis via lanosterol and 14-demethyllanosterol

21
Q

polyenes

A

inhibit ergosterols themselves

22
Q

How do polyenes kill?

A

act like AMPs to create pores

22
Q

How do polyenes kill?

A

act like AMPs to create pores

23
Q

Whats the issue with polyenes?

A

cross reactivity with mammalian cholesterol

24
Q

Are azoles and allylamines fungicidal or fungistatic and why?

A

fungistatic becuase inhibit ergosterol production so can’t grow

25
Q

nikkomycin

A

inhibits chintin synthase

26
Q

echinocandins

A

inhibit beta glucan synthase

27
Q

Why is it important to know species before treating?

A

Sensitivity and resistance to antifungals differ amongst species

28
Q

How does antifungal resistance occur?

A
  • eeffluc pump activation (common)
  • loss of target susceptibility via mutations (less common)

Eukaryotic Pathogens (15 decks)

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