LECTURE - Candida albicans Flashcards

1
Q

unicellular fungi that reproduce by budding or fission

A

yeast

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2
Q

yeast infections can be…

A

endogenous (almost exclusively endogenous; carrying infection yourself then cause infection) or exogenous

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3
Q

T or F. Yeasts are opportunists

A

T!

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4
Q

Candida species as normal flora

A

GI tract, oral cavities, and vagina

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5
Q

Candidosis

A

disease caused by Candida spp. (albicans mainly)

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6
Q

an emerging, antibiotic-resistant Candida organism

A

C. auris

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7
Q

agar for C. albicans

A

Sabouraud agar

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8
Q

C. albicans colonies

A

dry, pasty, white, and opaque
- budding cells that can produce pseudohyphae (produced in tissues; cant necessarily ee nice, unicellular buds) and chlamydospores depending on growth temp and medium on which they are grown

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9
Q

__% to ___% of healthy people have organisms in yeast as part of normal flora

A

30 to 50

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10
Q

T or F. Most C. albicans infections are exogenous

A

F, endogenous!

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11
Q

Three conditions to predispose to Candida albicans infections

A
  • compromised skin, excessive moisture, friction; invasive procedures like indwelling catheters
  • defects in Th1 mediated immunity (AIDS, cancer, etc.)
  • iatrogenic therapies
    > loss of normal flora via broad-spectrum antibiotics
    > damage to GI, GU, resp tract and loss of neutrophils due to cancer chemotherapy
    > changes in hormone levels such as use of BC
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12
Q

three main types of infections in C. albicans

A
  1. mucocutaneous
  2. cutaneous
  3. systemic candidiasis
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13
Q

mucocutaenous candidiasis

A
  • most common

- thrush, AIDS-associated oropharyngeal candidosis, vulvovaginal candidosis (vaginitis)

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14
Q

cutaneous candidiasis

A

skin and nails, prolonged exposure to moisture and heat, secondary to bacterial infection or loss of normal flora

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15
Q

systemic candidiasis

A
  • worst one!!
  • frequently fatal; nasty to get rid of once it has established; neutrophils VERY important (C. albicans not resistant to phagocytosis if they can be opsonized)
  • immunocompromised host; neutropenic, undergoing chemotherapy
  • often diagnosed post-mortem (SO MONITORING IS V IMPORTANT)
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16
Q

Treatment of C. albicans

A
  • azole family of anti-fungal drugs (fluconazole, ketoconazole, itraconazole)
  • topical treatments (nystatin, clotrimazole) are used for cutaneous or nail infections
  • oral drugs used for mucocutaneous candidiasis
  • IV drugs (amphotericin B) for severe infections
  • yeast cells may remain for 30 days following therapy
  • relapse is common (esp. bc ppl don’t stick to length of prescribed med)
17
Q

Why do we need to process specimen quickly for yeast?

A

they can proliferate rapidly (esp. in fluids)

18
Q

CHROMagar

A
  • differential

- can differentiate among diff Candida species

19
Q

germ tube test

A
  • lab ID for C. albicans
  • high protein media is inoculated with a small amount of yeast
  • tube is incubated for 2 hrs at 37 degrees C
  • a drop of media is examined microscopically under 10X and 40X for germ tubes
20
Q

sensitivity testing of C. albicans

A
  • used to test for susceptibility to anti-fungal drugs like fluconazole
  • standardized inoculum of pure culture incubated in each well containing doubling dilutions of a drug
  • plates read visually or spectrophotometrically
  • first well with yeast button = MIC (min. inhibitory conctn)
21
Q

C. albicans virulence factors

A

** after one of the three conditions that allow infection are met**
- attachment + biofilm formation (tissues and indwelling catheters)
> Hwp1 genes and ALS gene interaction w C-type lectin receptors on host cells
- organism switch from yeast to hyphal form with production of aspartyl proteases and phospholipase that lead to tissue damage and assist invasion

22
Q

Main PRR involved in recognizing Candida albicans

A
  • mannose-bindng lectin
  • membrane-bound C-type lectin receptors macrophage mannose receptor 1 (MMR)
  • dendritic cell-specific ICAM-3… (DC-SIGN)
  • macrophage-inducible C-type lectin (MINCLE)
  • TLR4
  • TLR2
  • TLR9 in cytosol can recognize fungal DNA
23
Q

Pathogenesis of C. albicans

A
  • surface glucomannan receptors on the yeast bind to fibronectin covering epithelial cell or to elements of the extracell matrix
  • when epithelial surface is lost or C. albicans have invaded beyond it, invasion is associated with formation of hyphae + proteinase production = digests tissue elements
24
Q

C. albicans tissue invasion

A
  • adhesion to epithelium
  • epithelial penetration and invasion by hyphae
  • vascular dissemination, which involves…
  • hyphal penetration of blood vessels and seeding of yeast cells into the bloodstream;
  • endothelial colonization and penetration during disseminated disease
25
Q

fourth most common organism recovered from blood in hospitalized patients

A

C. albicans

- it can disseminate widely when entering the bloodstream and can be found in any organ

26
Q

The Dalmau Test

A
  • for chlamydospores

- test conditions: media, temperature, air, surface tension, length of incubation

27
Q

thick-walled resting spores

A

chlamydospores

28
Q

filamentous growth from Dalmau test

A

C. parapsilosis

29
Q

chlamydospores from Dalmau test

A

C. albicans

30
Q

segmented pseudohyphae from Dalmau test

A

C. tropicalis

31
Q

Biochemical Id methods for Candida

A
  • assimilation
  • based on carbs that are used as sole carbon sources
  • automated or manual test
  • gold standard is API 20C