Mycology

Question 1

Describe the recommended storage conditions for a clinical specimen that has been collected for fungal analysis and will not reach the laboratory within 2 hrs of collection?

Answer 1

• Store at 4C

- Room temp for skin, nail, hair bc dermatophytes & mucorales are sensitive to cold

Question 2

Describe the recommended protocol for the collection of a specimen for fungal analysis including the minimum quantity required?

Answer 2

1. Wipe area w/ alcohol wipe
2. Scrape the advancing margin (where active)
   * nails: collect underneath
   * Min sample: top of a push pin

Question 3

Which part of the infection site should be sampled?

Answer 3

Margin where active. Not centrewhere contaminated w/ saprophytes

Question 4

If a fungal agar contains cycloheximide, what primary group of fungi is the media selecting for?

Answer 4

cycloheximide suppresses contaminating fungi and allows actinomycetes to grow

Question 5

Cycloheximide can also be used to select for dimorphic fungi but it only allows all of the dimorphic fungi to grow at a certain temperature. Is it RT or 37˚C?

Answer 5

.? both?

- Yeast = 37ºC

Question 6

What is the purpose of incorporating 10% KOH in the wet mount medium for fungal specimens?

Answer 6

• Clears keratin
• Separate cells
• Helps detection and examination

Question 7

As a medical scientist, what additional steps could you do in the presence of a sterile fluid with moderate to abundant leucocytes and no organisms seen? *

Answer 7

• Concentrate by centrifugation?

Question 8

The meaning of a true pathogen & Give an example of an true fungal pathogen (genus + species)?

Answer 8

True pathogen: always a disease causing pathogen in all exposed individuals
e.g. Histoplasma capsulatum

Question 9

If a fungal structure is described as being either ‘hyalo’ or ‘phaeo’, what
does this mean?

Answer 9

Hyalo: light coloured
Phaeo: dark coloured

Question 10

Name the 3 divisions that are

known to contain clinically relevant fungi?

Answer 10

Ascomycota
Basidiomycota
Mucoromycota (aka Zygomycota)

Question 11

The members of the Mucoromycota all share two distinctive microscopic features.
What are they?

Answer 11

Coenocytic hyphae & Sporangium

Question 12

What is it, and what does it mean, if a member of the Ascomycota can produce anascocarp?

Answer 12

ascocarp: 4-8 sexual spores (ascospores) contained in smaller sacs (asci) = ascocarp

Question 13

To which phyla/division does the genus Cryptococcus belong?

Answer 13

Basidiomycota

Question 14

What determines whether an organism

belongs to Fungi imperfecti’ group?

Answer 14

Sexual repro. not known?

Question 15

Name the 3 sub-groups within the ‘Fungi imperfecti’?

Answer 15

• Blastomycetes: repro. by budding
• Coelomycetes: Moulds that produce conidia w/in cavity of fungal tissue (condioma)
• Hyphomycetes: Moulds that produce conidia w/out fruiting hyphae or produce only sterile hyphae

Question 16

What is the main

difference between the dematiaceous and hyaline hyphomycetes?

Answer 16

Hyaline: Colourless/brightly coloured colonies
Dematiaceous: Dark black/brown pigmented colonies

Question 17

How do fungi obtain nutrition from an organic substrate?

Answer 17

Fungi excrete enzymes onto external substrate => complex => simple molecules (nutrients) absorbed via cell wall