fungi

Question 1

label the structures on the diagram below of fungi

Answer 1

Question 2

describe the structure and poroperties of fungi

Answer 2

• Eukaryotic
• Grow at 25ºC (some at 37º)
• Non-photosynthetic
• Cell walls contain chitin and other polysaccharides
• Heterotrophic nutrition- uses exoenzymes to digest outside and then absorbs nutrients
• Can reproduce sexually and asexually
• Tolerate high osmolality and low pH
• Resistant to antibacterial drugs

Question 3

describe mould hyphal growth

Answer 3

Mould form large colonies. They can produce asexual spores in different ways. Sexual spore- ascospores, basidiospores, zygospores are also important in taxonomy.

Question 4

describe yeast growth

Answer 4

Yeast divide asexually by budding but can also have sexual reproduction.

Question 5

what are the common morphological forms of fungi

Answer 5

Yeasts- oval/spherical appearance

Moulds- filamentous fungi- hyphal forms

Dimorphic fungi- will grow in yeast or hyphal forms dependant of the temperature of growth.

Question 6

how do fungi reproduce

Answer 6

• many can reproduce both sexually and asexually
• sporulation bodies can be used for identification in clinical samples
• spores are relativelty resistant and can survive and spread infection (survive disinfection)

there are 2 main types of asexual spores
condida formed on condiophores
sporangiospores formed on sporangiophores

Question 7

what media is required for fungal culture and why

Answer 7

sabouraud dextrose media
- has a slightly acidic pH (5.6)
- inhibitory antibiotics are often added to prevent bacterial contamination
-

Question 8

What are the growth times and temperatures for different fungal groups?

Answer 8

Fungi are cultured at both 25 and 37°C this helps describe if they are dimorphic or not.

Question 9

How are fungi differentiated?

Answer 9

colonial characteristics- size appearance after set time, colour both sides, surface elevation depressions, other patterns.

Examination of spore structures- from culture, from clinical sample

Features of vegetative hyphae- presence or absence of septa, hyaline (colourless) or dematiaceous (pigmented), hyphal structures- spiral, racket space.

Question 10

describe ringworm

Answer 10

• circular skin lesions caused by dermatophytes
• colonize and invade skin, hair and nails
• spores shed from infected animals remain infective for many months
• transmitted by contact or contaminated surfaces

Question 11

describe malassezia pachydermatis

Answer 11

• yeast (unicellular, peanut shaped cells)
• commensal on skin
• associated with canine skin and ear infections
• opportunisitc pathogens

Question 12

describe aspergillus

Answer 12

• filamentous mould with septated hyaline hyphae and condida formed on condiophores
• ubiquitous
• rapidly growing pigmented colonies
• respiratory pathogen, acquired by inhalation of spores
• invasive

in dogs: sinonasal aspergillosis invades nasal mucosa and turbinate bones. needs to be removed