3 Fungi (Host Pathogen Interaction)

Question 1

Major Fungal Groups (Characteristics)

Answer 1

• Eukaryotic
• Mostly found in soil or water w/decaying organic matter
• Candida sp part of normal human flora

Question 2

Cell wall and membrane components

Answer 2

• Contain polymer of N-acetylglucosamine called CHITIN (Beta 1-4 linkage)
• Beta-Glucans provide cell rigidity/shape
• Membrane contains ERGOSTEROL

Question 3

Types of fungal growth

Answer 3

• Filamentous fungi: MYCELIUM (mold like)
• Yeast like fungi: BUDDING reproduction
• Dimorphic fungi: can grow mold like or yeast like depending on enviroment

Question 4

Sporulation

Answer 4

• Principle means by which fungi reproduce
• Resistant and can go airborne
• Asexual sporulation: conidia formed by mitosis in/on conidiophores (major fungal infection source)
• Sexual sporulation: Ascospores formed by meiosis (used to identify fungi)

Question 5

Cutaneous mycoses

Answer 5

-Cause of many common skin diseases: athletes foot (tinea pedis), ringworm (tinea corporis), jock itch (tinea cruris)

Question 6

Subcutaneous mycoses

Answer 6

-Infections of the dermis, subcutaneous tissue, bone: found in soil/vegetation, laceration or puncture wound

Question 7

Systemic mycoses

Answer 7

• Disease in immunocompetent hosts

- Dimorphic: mycelium form in culture; yeast form in tissue

Question 8

Opportunistic mycoses

Answer 8

• Disease in immunocompromised/severe trauma patients

- Nosocomial infections (hospital infections)

Question 9

Challenges in treating fungal infections

Answer 9

• RESISTANCE to antifungals
• TOXICITY to antifungals
• Fungi are EUKARYOTES
• IDENTIFICATION of fungi

Question 10

Commonly used antifungals

Answer 10

• Polyenes: binds ergosterol (eg nystatin, amphotericin B)
• Azoles: inhibit ergosterol biosynthesis
• Echinochandins: inhibit 1,3-Beta-glucan synthesis (cell wall)