Lecture 6 Flashcards
Fungi
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
Two Fungi Forms:
- Yeasts = Single celled, reproduce from budding
- Molds = Multi, Filamentous Structures (thin branched hyphae and complex networks/ mycelium)
Reproduce via spore (not same as bacterial spores)
Dimorphic
Alternate between yeast and mold form depending on environment
3 General types of fungal diseases
- Hypersensitivity Diseases (allergic response not a true infectious disease)
- Mycotoxicosis
Poisoning due to consumption of fungal metabolic product - Mycoses
Infection due to growth of fungus in or on human host
Types of Mycoses
- Cutaneous (superficial)Mycoses
- Growth on body
- Physical contact
Caused by dermatophytes (fungi use keratin as nutrient) - Subcutaneous mycoses
- Deeper skin/ cuts or wounds - Systemic (deep) mycoses
- Internal organs
- start in lungs (severe)
Candida
Yeast as part of normal human flora
Cause Candidiasis:
- Change in immune status
- Body Defenses breached
Coccidioides
- 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)
Lab Diagnosis of Fungal Infections
- Direct Microscopic exams
2. Growth on culture media + biochemical identification
Anti Fungal Agents
Fungi are eukaryotic/ Selective toxicity difficult (same as host)
Agents topical
Most target fungal cell envelope or NA synthesis
Polyenes (Amphotericin B, Nystatin)
Bind to ergosterol -> Create pores in fungal plasma membrane
Azoles
Block ergosterol(membrane component) synthesis = Defective membranes lead to leakage of cytoplasmic contents
Nucleotide Analogues
- inhibitor of DNA/RNA synthesis
- Converted to active form by fungal enzymes-> blocks NA synthesis
- Less toxic/ humans lack ability to transport flucytosine
Parasites (2 types)
Lifecycle depends on host
- Protozoa
- single celled
- similar to yeast - Helminths
- Micro/macroscopic
- multi-cellular
- complex body structures
Protozoa
Two forms
Trophozoite = Metabolically active, replicating found inside of host
Cyst= Dormant, non-replicating, thicken wall to survive
-form which is transmitted
Helminths
Usually macroscopic/ complex body structures
Nematodes, tapeworms, flukes
Helminths
Reproduce via eggs
Eggs/larvae = infective forms
Adult worms= Cause symptoms of disease
-obstruct or displace
Tissue degrading enzymes
- Interfere with nutrients
Giardia Lamblia (Giardiasis)
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
Naegleria Fowleri / Amoebic Meningitis
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)
PinWorms
Kids
Mild diarrhea and intense rectal itching
Females lay eggs around perianal area
Diagnosed by pinworm paddles
Anti Parasitic Agents
interfere with protozoan biosynthetic pathways or with helminth neuromuscular functions
