LECTURE - Candida albicans

Question 1

unicellular fungi that reproduce by budding or fission

Answer 1

yeast

Question 2

yeast infections can be…

Answer 2

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

Question 3

T or F. Yeasts are opportunists

Answer 3

T!

Question 4

Candida species as normal flora

Answer 4

GI tract, oral cavities, and vagina

Question 5

Candidosis

Answer 5

disease caused by Candida spp. (albicans mainly)

Question 6

an emerging, antibiotic-resistant Candida organism

Answer 6

C. auris

Question 7

agar for C. albicans

Answer 7

Sabouraud agar

Question 8

C. albicans colonies

Answer 8

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

Question 9

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

Answer 9

30 to 50

Question 10

T or F. Most C. albicans infections are exogenous

Answer 10

F, endogenous!

Question 11

Three conditions to predispose to Candida albicans infections

Answer 11

• 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

Question 12

three main types of infections in C. albicans

Answer 12

1. mucocutaneous
2. cutaneous
3. systemic candidiasis

Question 13

mucocutaenous candidiasis

Answer 13

• most common

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

Question 14

cutaneous candidiasis

Answer 14

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

Question 15

systemic candidiasis

Answer 15

• 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)

Question 16

Treatment of C. albicans

Answer 16

• 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)

Question 17

Why do we need to process specimen quickly for yeast?

Answer 17

they can proliferate rapidly (esp. in fluids)

Question 18

CHROMagar

Answer 18

• differential

- can differentiate among diff Candida species

Question 19

germ tube test

Answer 19

• 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

Question 20

sensitivity testing of C. albicans

Answer 20

• 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)

Question 21

C. albicans virulence factors

Answer 21

** 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

Question 22

Main PRR involved in recognizing Candida albicans

Answer 22

• 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

Question 23

Pathogenesis of C. albicans

Answer 23

• 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

Question 24

C. albicans tissue invasion

Answer 24

• 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

Question 25

fourth most common organism recovered from blood in hospitalized patients

Answer 25

C. albicans

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

Question 26

The Dalmau Test

Answer 26

• for chlamydospores

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

Question 27

thick-walled resting spores

Answer 27

chlamydospores

Question 28

filamentous growth from Dalmau test

Answer 28

C. parapsilosis

Question 29

chlamydospores from Dalmau test

Answer 29

C. albicans

Question 30

segmented pseudohyphae from Dalmau test

Answer 30

C. tropicalis

Question 31

Biochemical Id methods for Candida

Answer 31

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