6. Fungi and Fungal Infections Flashcards
1
Q
What are some important features of fungi?
A
- Eukaryotes
- Free-living
- Spore-bearing
- Absorptive nutrition
- Lack chlorophyll
- Sexual and asexual reprodution
- Cell wall of chitin
- Most are aerobes or facultative aerobes
2
Q
What are yeast?
A
- Single-celled fungi
- Divide by fission or by budding
- Form colonies similar to bacteria
- Facultative aerobes
3
Q
What is a mould?
A
- Multicellular, filamentous fungi
Made up of: - Hyphae: long filaments of cells joined together
- Thallus: body of the mould (made up of many hyphae)
- Mycelium: large, visible, filamentous mass made up of many hyphae
Growth: - hyphae grow by elongating at the tips
4
Q
What does it mean when a fungi is dimophic?
A
- It means it can exist as multicellular fungi (moulds) or single-celled (yeasts)
- Feature of many pathogenic fungi, usually dependent on temperature:
- At 37 degrees: yeast form (reproduce by budding)
- At 25 degrees: mould form (produce aerial and vegetative hyphae)
5
Q
Can fungi be haploid or diploid?
A
- Yes, they are usually in haploid state but can form a diploid nucleus during sexual reproduction
6
Q
How do fungal spores differ from bacterial spores?
A
- 1 spore gives rise to a mycelium (bacterial spores give rise to 1 bacterial cell)
- Produced as part of asexual or sexual reproduction (bacterial spores are formed to survive unfavouble conditions
7
Q
How are fungi diagnosed in the lab?
A
- Direct examination:
- Large size, distinct morphological features
- Lactophenol cotton blue - Culturing
- Antigen and Antibody detection
8
Q
Are fungi primarily pathogenic?
A
- No, they are widely distributed in the environment and some are part of normal flora
- Of over 100,000 fungal species only 200 are linked to disease in animals (they are primarily plant pathogens)
- Humans are relatively resistant, only immunocompromised individuals are at high risk
- Human mycoses (fungal infections) are caused by true fungl pathogens and opportunistic pathogens
9
Q
What is the key adaption of fungi that can be infectious agents?
A
- Thermal dimophism- the ability to switch from hyphal cells in environment to yeast cells within the animal body
10
Q
What are the 5 groups of pathogenic fungi?
- How do you get these infections?
A
- Direct contact:
1. Superficial: contamination of skin surface
- Cutaneous: contamination of skin surface
- Subcutaneous:
incoculated skin, trauma - Systemic infections: have disseminated to visceral tissues (acquired through inhalation of spores)
- Opportunistic mycoses:
includes Candida, Aspergillus, Cryptococcus and Zygomycota (occur under specific conditions)
11
Q
What are the most common types of Fungal Mycoses?
A
- Dermaphytoses:
a superficial pathogenic fungus that grows on skin, mucous membranes, hair, nails, feathers, and other body surfaces, causing ringworm and related diseases e.g Tinea - Dermatophyte genera:
1. Trichophyton: hair, skin, nails
2. Microsporon: scalp and skin (not nails)
3. Epidermophyton: skin and nails
12
Q
What are cutaneous fungi mycoses?
A
- Infections strictly confined to keratinized epidermis (skin, hair, nails)
- Also called dermatophytoses: includes ringworm and tinea
- Infection is facilitated by moist, chafed skin
- Causes a long infection followed by localised inflammation and allergic reaction to fungal proteins
- Called ringworm infections
13
Q
How is Tinea corporis treated?
A
- Tinea corporis = ringworm of the body
- Treated with topical agent
- Severe widespread cases require systemic griseofulvin treatment
14
Q
What is invasive candidiasis?
A
- Usually begins with a normal yeast infection
- If the body has a functioning phagocytic response the infection stops there- if not the infection spreads to many organs and can cause mortality
15
Q
What are the main virulence factors of pathogenic fungi?
A
- Thermal dimorphism
- Toxin production
- Capules and adhesion factors
- Hydrolytic enzymes
- Inflammatory stimulants
