Fungal Infections

Question 1

What are fungi?

Answer 1

Eukaryotic living organisms divided into unicellular and multicellular. Only 12 species colonise humans

Question 2

What are the features of fungi?

Answer 2

Eukaryote with membrane bound nucleus and 80s ribosome. It has a cell wall formed of chitin with glucan or glycoproteins which is a target of anti-fungal treatment. It has an ergosterol plasma membrane

Question 3

What is a spore?

Answer 3

One celled reproductive unit which can give rise to other units without sexual fusion

Question 4

What is the feature of fungi plasma membrane?

Answer 4

Phospholipid bilayer stabilised by the molecule ergosterol, a steroid molecule that has an identical role to cholesterol in reducing fluidity

Question 5

What is a hypha?

Answer 5

Thread-like filaments and tubes in the fungi that make up the root of the fungi called the mycelium. They increase in size via apical growth at the tip to form candida spores

Question 6

What are candida?

Answer 6

Spores that form via asexual reproduction from the tip of a hyphae in both unicellular and multicellular fungi.

Question 7

What are the unicellular fungi?

Answer 7

Yeast and mould which reproduce by budding

Question 8

What are the multicellular fungi?

Answer 8

Mushrooms and mould which reproduce by sexual reproduction.

Question 9

What are saprocytes?

Answer 9

Organisms which feed on dead matter

Question 10

How can fungi cause disease?

Answer 10

Act as opportunistic pathogens when the immune system is compromised. It can act as a secondary pathogen that causes infection following changes to the immune system through treatment such as antibiotics.

Question 11

What makes fungi unsuitable to disease in humans?

Answer 11

Ill-adapted to growth at 37 degrees celsius or using human nutrients
Slow growing
Innate defence system acts against pathogenic fungi using IL-7 and PAMP and neutrophil traps
Enxymatic pathways are most efficient in non living substrates

Question 12

Which groups are most vulnerable to fungal infections?

Answer 12

Immunocompromised groups such as those with diabetes, pregnancy, taking steroids, chemotherapy due to being ubiquitous in the environment. Inhalation of fungi occurs everyday

Question 13

What is an anamorph?

Answer 13

Asexual form of fungi

Question 14

What is the asexual reproduction in fungi?

Answer 14

Nuclear fission occurs followed by either fragmentation, budding or spore formation

Question 15

What is fungal fragmentation?

Answer 15

Mycelium separates into smaller components via mitosis and these individual components form new mycelium.

Question 16

What is fungal budding?

Answer 16

Bulge forms on the side of the progenitor which divides by cytokinesis to then elongate and form new fungi

Question 17

How do spores form?

Answer 17

Spores that are produced directly from the fungi are sporangium spores
Spores that are produced from the apical tip of the hyphae are condida

Question 18

What is sexual reproduction in fungi?

Answer 18

Nuclear fission occurs
Plasmogamy where two haploid cells fuse and coexist in dikaryotic stage
Karyogamy where the haploid nuclei fuse into diploid karyotic cell
Meiosis occurs in the sexual gametogenic organs of the fungi

Question 19

What is homothallic?

Answer 19

Sexual reproduction between two identical mycelium

Question 20

What is heterothallic?

Answer 20

Sexual reproduction between two different mycelium

Question 21

What is yeast?

Answer 21

Unicellular infectious fungi with a round or ovoid shape. It reproduces asexually or sexual reproduction to form ascospores. It has a chitin-beta galactan cell wall and is fast growing

Question 22

What is the pathogenic yeast?

Answer 22

Candida species and cryptococcus neoformans which is in an ovoid shape for travel around the body. Hyphae and pseudohyphae shape is ideal for invasive infection into tissues

Question 23

What is candida albicans?

Answer 23

Opportunistic pathogenic yeast which can form both true and pseudohyphae

Question 24

What is cryptococcus neoformans?

Answer 24

Round ovioid yeast cells transmitted from bird droppings and causes meningitis.

Question 25

What is mould?

Answer 25

Multicellular fungi which grow via formation of hyphae via sexual reprodution via spores or asexual reproduction via conidia spores. It has a gallactoman-chitin cell wall and is slow growing

Question 26

What is the pathogenic mould?

Answer 26

Aspergilius which can cause pneumonia.

Question 27

What is a dimorphic fungi?

Answer 27

Fungi which alternates between infectious fungi or sapprophytic mould depending on temperature.

Coccidiodomyocosis is a dimorphic fungi is acquired via inhalation of spores and disseminates to other organs. Can cause deep mycoses via spore inhalation

Question 28

How can yeast and mould be differentiated

Answer 28

Yeast can be seen in microscopy, PCR, fast growing and beta-galactan cell wall.

Mould is slow growing, present on tissue and galactoman cell wall and PCR is inconclusive.

Question 29

What is mycoses?

Answer 29

Fungal infection

Question 30

What is a superficial mycoses?

Answer 30

Occurs in the outerost layer of the epidermis and hair. There is no invasion of tissue so no pathological changes and no immune response is evoked

Question 31

What is a cutaneous mycoses?

Answer 31

Fungal infection restriction to the keratinised layers of the skin, hair and nails. Immune response is evoked if it penetrates deeper layer of the skin

Question 32

What is an example of a superficial mycoses?

Answer 32

Tinea versicolour

Dermatophytosis.

Question 33

What is Tinea versicolour?

Answer 33

Tinea versicolour, a superficial myoces by Malasezzia fur fur which produces azelaic acid that produces bleaching/lightening effect of skin colour

Question 34

What is dermatophytosis?

Answer 34

AKA ringworm, which is a superficial mycoses which uses keratin as a nutrient. There is NO itching and it occurs anywhere on the body.

Question 35

What is subcutaneous mycoses?

Answer 35

Initiated by piercing trauma which allows fungi to enter the dermis, subcutaneous tissue, muscle and fascia layers. May cause chronic infection which are locally invasive.

It is difficult to treat and may require surgical intervention. Usually found in the tropic and subtropic region.

Question 36

What is the most common deep mycoses?

Answer 36

Aspergillus which has an angiotrophic effect of invading blood vessels and causing pulmonary haemorrhage/infarction. This occurs in severely immunocompromised patients.

Question 37

What is candiadis?

Answer 37

Most common mycoses which can be superficial or cutaneous mycoses: Forms part of normal flora in vagina and in the mouth. When epithelial barrier is damaged they can infect superficially. Becomes systemic infection in immunocompromised patients.

Question 38

What are the groups of dermatophysis?

Answer 38

Geophilic: contact with soil
Anthrophilic: contact with humans
Zoophilic: contact with animals

Question 39

What are the classes of anti-fungals?

Answer 39

Amhpotecerin
Azoles
Echinocandins

Question 40

How does amphotecerin work?

Answer 40

Bind to ergosterol and causes a pore to form which allows leakage of intracellular ions

Question 41

How does azole work?

Answer 41

Inhibits lanosterol demythelase from lanosterol -> ergosterol. Causes depletion of ergosterol which inhibtis fungal growth. Examples include fluconazole.

Question 42

How does echinocandins work?

Answer 42

Inhibits synthesis of glucan in the cell wall of fungi for systemic fungal infection in immunocompromised groups.

Question 43

How is candida albicans identified?

Answer 43

Formation of true hyphae

Question 44

What is a mycotoxin?

Answer 44

Toxin produced by a fungi. Can lead to ergotism where there is contamination of food with fungi which causes severe painful seizures

Question 45

What is the most common deep mycoses?

Answer 45

Aspergillus fumatigus due to spore inhalation which is the most ubiqutous in the environment