Lecture 6

Question 1

Fungi

Answer 1

Uni/Multi Cellular

Fungal Cell Envelope:

1) Ergosterol - Sterol compound found in fungal PM
2) Chitin - rigid multi layered Carb structure (Similar to pg) lying above PM

Question 2

Two Fungi Forms:

Answer 2

1. Yeasts = Single celled, reproduce from budding
2. Molds = Multi, Filamentous Structures (thin branched hyphae and complex networks/ mycelium)

Reproduce via spore (not same as bacterial spores)

Question 3

Dimorphic

Answer 3

Alternate between yeast and mold form depending on environment

Question 4

3 General types of fungal diseases

Answer 4

1. Hypersensitivity Diseases (allergic response not a true infectious disease)
2. Mycotoxicosis
   Poisoning due to consumption of fungal metabolic product
3. Mycoses
   Infection due to growth of fungus in or on human host

Question 5

Types of Mycoses

Answer 5

1. Cutaneous (superficial)Mycoses
   - Growth on body
   - Physical contact
   Caused by dermatophytes (fungi use keratin as nutrient)
2. Subcutaneous mycoses
   - Deeper skin/ cuts or wounds
3. Systemic (deep) mycoses
   - Internal organs
   - start in lungs (severe)

Question 6

Candida

Answer 6

Yeast as part of normal human flora

Cause Candidiasis:

• Change in immune status
• Body Defenses breached

Question 7

Coccidioides

Answer 7

• Dimorphic fungus (warm dry areas)
• Grow as hyphae at 20-25degrees and release arthospores (hyphal frags) into the air

-Inhaled / body temp triggers spherules (spores)

Question 8

Lab Diagnosis of Fungal Infections

Answer 8

1. Direct Microscopic exams

2. Growth on culture media + biochemical identification

Question 9

Anti Fungal Agents

Answer 9

Fungi are eukaryotic/ Selective toxicity difficult (same as host)

Agents topical

Most target fungal cell envelope or NA synthesis

Question 10

Polyenes (Amphotericin B, Nystatin)

Answer 10

Bind to ergosterol -> Create pores in fungal plasma membrane

Question 11

Azoles

Answer 11

Block ergosterol(membrane component) synthesis = Defective membranes lead to leakage of cytoplasmic contents

Question 12

Nucleotide Analogues

Answer 12

• inhibitor of DNA/RNA synthesis
• Converted to active form by fungal enzymes-> blocks NA synthesis
• Less toxic/ humans lack ability to transport flucytosine

Question 13

Parasites (2 types)

Answer 13

Lifecycle depends on host

1. Protozoa
   - single celled
   - similar to yeast
2. Helminths
   - Micro/macroscopic
   - multi-cellular
   - complex body structures

Question 14

Protozoa

Answer 14

Two forms

Trophozoite = Metabolically active, replicating found inside of host

Cyst= Dormant, non-replicating, thicken wall to survive
-form which is transmitted

Question 15

Helminths

Answer 15

Usually macroscopic/ complex body structures

Nematodes, tapeworms, flukes

Question 16

Helminths

Answer 16

Reproduce via eggs

Eggs/larvae = infective forms

Adult worms= Cause symptoms of disease
-obstruct or displace
Tissue degrading enzymes
- Interfere with nutrients

Question 17

Giardia Lamblia (Giardiasis)

Answer 17

Abdominal cramping, belching, nausea, flatulence, diarrhea

Fecal- oral route:
More common/ Water contaminated cysts
Less common/ Feces Contact

Cyst ingested - wall degrades - converts to trophozoite inside of intestinal tract

Multiply

Dehydration of stool - converts to cyst -back to environment

Question 18

Naegleria Fowleri / Amoebic Meningitis

Answer 18

CNS infection
Warm water

Cyst form + two trophozoite forms (amoeboid or flagellate)

Amoeboid infective form

Eats brain though nostril (only type of contact to cause infection)

Question 19

PinWorms

Answer 19

Kids
Mild diarrhea and intense rectal itching

Females lay eggs around perianal area

Diagnosed by pinworm paddles

Question 20

Anti Parasitic Agents

Answer 20

interfere with protozoan biosynthetic pathways or with helminth neuromuscular functions