7. Oral Fungal Infections, Candida

Question 1

55. Candidiasis (like most fungal infections) usually results from defects in ___________ and/or lack of _______________.

Answer 1

Defects in normal host defense and/or lack of competitive normal flora

Question 2

56. Fungi are eukaryotes and have similar structures to other eukaryotic cells. This means there are few anti-fungals available to treat fungal infections (due to auto-interactions). One big difference is the cell membrane however. What is that difference?

Answer 2

Fungi cell wall contains ergostal instead of cholesterol. Antifungal strategies have been developed based on the presence of ergostal in the fungal cell wall.

Question 3

56. What are two examples of drug types that we use in anti-fungal therapies?

Answer 3

1. Azoles - Inhibit ergosterol synthesis

2. Polyenes - Bind and form pores in ergosterol-containing membranes

Question 4

56. What are the two basic morphologies of fungi?

What does it mean that some fungi are dimorphic?

Answer 4

1. Yeasts (single cells)
2. Hyphae (filamentous) - multinucleated branched, mold like

Dimorphic - Can exist in both a filamentous or yeast morphology depending on the environmental conditions of growth

Question 5

56. Why is the morphology of Candida albicans described as complicated and fairly unique?

Answer 5

In addition to being referred to as dimorphic, they can assume a psuedohyphae morphology where the cells are elongated and linked like sausages (So Candida is actually polymorphic!)

Question 6

58. In general, healthy people have a sufficient level of innate immunity to fungal diseases. What are the aspects of innate host resistance that contributes to this immunity?

Answer 6

1. Intact, functioning epithelium (primary barrier)

2. Fatty acids, pH, epithelial cell turnover, and the normal bacterial flora

Question 7

58. Fungal pathologies

- What is mycotoxicoses?

Answer 7

Poisoning from mycotoxins (toxins from fungi)

Question 8

58. Fungal pathologies

- What are some examples of hypersensitivities that can result from fungi?

Answer 8

1. Hay Fever and Asthma (Type 1 hyper.)

2. Contact dermatitis to fungal products (Type 4)

Question 9

58. Fungal pathologies - Where do the following mycoses (fungal infections) occur?
    - Superficial mycoses
    - Cutaenous mycoses
    - Subcutaneous mycoses

Answer 9

• Superficial - Outermost skin layers, hair
• Cutaenous - Skin and nails (tinea capitis at the scalp)
• Subcutaenous mycoses - Fungi/spores introduced via wounds

Question 10

58. Fungal pathologies - What are examples of the following mycoses (fungal infections)?
    - Systemic mycoses
    - Opportunistic mycoses

Answer 10

• Systemic - Lung infections (inhaled spores) - similar to tuberculosis
• Opportunistic (immunocompromised) - Candidiasis, cryptococcus (bird droppings to lung), aspergillosis (soil to lungs), pneumocystis (lung infection in AIDS)

Question 11

59. What are three reasons as to why opportunistic mycoses are of growing concern?

Answer 11

1. AIDS
2. Growing use of immunosuppressive therapies (cancer, transplants, autoimmunity)
3. Use of broad-spectrum antibiotics

These mycoses should only cause serious disease under unusual circumstances (usually host debilitation)

Question 12

59. What is a fungal disease that is a major problem for immunocompromised hosts?
    - Do most humans come into contact with the fungi that cause this disease?

Answer 12

Candidiasis (such as C. albicans)

It is part of the normal flora of many humans (so yes).

Question 13

61. What are predisposing risk factors for candidiasis?

Answer 13

1. Being young / infant
2. Elderly
3. Debilitated (endocrine imbalance, decrease phagocytes, T cell defects, chemotherapy to decrease saliva, steroid therapy (inhalers), antibiotics, HIV)
4. Oral appliance (incorrect cleaning)
5. Catheters

Question 14

63. Describe normal T-cell mediated (cellular) response to fungal infections
    - What is the first chemical released that signals the rest of the immune response?
    - The released chemical lead to what three responses?

Answer 14

Th cells respond to fungal antigens by producing cytokines
- The cytokines cause an immune response:
A. Inflammation
B. Recruit and activate phagocytic cells
C. Stimulate epithelial cell turnover

Question 15

64. Describe the psuedomembrane that can form during a candidiasis infection
    - Loosely or firmly attached
    - Made of what cells

Answer 15

Loosely attached (contrasts with diptheria, which is hard to remove)

Made of PMNs, dead PMNs, fibrin, and fungal cells

Question 16

65. What are the four primary clinical presentations of oral candidiasis?

Answer 16

Primary oral candidiasis

1. Acute pseudomembranous (thrush)
2. Erythematous (red inflammation)
   - Acute atrophic
   - Chronic atrophic (unclean denture)
3. Chronic hyperplastic
4. Chronic mucocutaenous (rare, immune defect)

Question 17

65. What is an example of a secondary clinical presentation of oral candidiasis?

Answer 17

Systemic mucocutaenous candidal infections - (immune defect)