Fungal Infections

Question 1

What are the two main phyla of fungi?

Answer 1

Ascomycota

Basidiomycota

Question 2

Which fungus out of the basidiomycetes causes the largest burden of disease?

Answer 2

Cryptococcus neoformans and Cryptococcus gatii

Cryptococcus neoformans Causes cryptococcal meningitis

Question 3

What three types of illness do fungi cause?

Answer 3

Allergies
Mycotoxicoses
Mycoses

Question 4

Define mycotoxicosis.

Answer 4

A toxic reaction to the ingestion/inhalation of toxins produced by fungi

Question 5

What is known as the most carcinogenic natural compounds and what produces it?

Answer 5

Aflatoxin – Aspergillus flavus

causes liver damage from hep B, then predisposes to liver cancer

Question 6

Define mycosis.

Answer 6

Disease caused by fungi that is classified based on the level of tissue affected

Question 7

What are the four types of mycosis?

Answer 7

Superficial
Cutaneous
Subcutaneous
Systemic

Question 8

What are superficial mycoses? Give some examples.

Answer 8

Mycoses that affect the skin and hair

No tissue is invaded so there is no cellular response

Black piedra
White piedra
Dandruff
Tinea nigra

Question 9

What are cutaneous mycoses? Give some examples.

Answer 9

Produce keratinases which hydrolyse keratin – causes inflammation

Trychopyton and Microsporum are main examples

Other examples:
Tinea capitis
- common child infection

tinea pedis
- very common

Tinea corporis
ring worm

Question 10

What are subcutaneous mycoses?

Answer 10

Chronic, localised infections of the skin and subcutaneous tissue following traumatic implantation of the aetiological agent.

Question 11

What type of fungal infection is a big problem in transplant settings?

Answer 11

Aspegillosis

There is a very high mortality for systemic mycoses

Question 12

What are the three types of candida infection that can occur in the immunocompromised?

Answer 12

Mucosal
Systemic
Superficial

Question 13

What are the three types of mucocutaneous candidiasis that occurs in people with HIV?

Answer 13

Oesophageal
Vulvovaginal
Oropharyngeal

high mortaility rates once the disease is systemic

Question 14

What are the main risk factors for systemic candida infections?

Answer 14

Chemotherapy
Gut-related surgery
Catheters

• not seen in healthy humans

Question 15

What are the three main targets for antifungal therapy?

Answer 15

• Cell membrane - use ergosterol instead of cholesterol
• DNA synthesis
• Cell wall

Question 16

How do antifungals that target the cell membrane work? Give some examples.

Answer 16

• Fungal cell membranes contain ergosterol instead of cholesterol
• Some antifungals inhibits ergosterol synthesis

Examples: azole this is the main drug group (itraconazole)= drug

Question 17

How do antifungals that target DNA synthesis work? Give an example.

Answer 17

Pyrimidine analogues are used to interfere with DNA synthesis
Example: Flucytosine (used for Cryptococcus)

Question 18

How do antifungals that target the cell wall work? Give an example.

Answer 18

• They inhibit the assembly of specific fungal cell wall components such as glucans and chitin
• The uniqueness of the structure makes a premier target for antifungal therapy

Example: Caspofungin (a type of Echinocandin)

Question 19

What components are found in fungal cell walls but not in mammalian cell walls?

Answer 19

Glucan

Chitin

Question 20

what are general features of fungi?

Answer 20

• they are eukaryotes

- they have several chromosomes and a massive gene complex

Question 21

what are most fungal infections?

Answer 21

• ascomycetes

Question 22

where might the cyrptococci go?

Answer 22

• into the lungs although alveolar macrophages are good at destroying them
• if they get into the sugar rich brain then might cause meningitis

Question 23

how do fungi digest their food?

Answer 23

• extracellularly
• They produce hydrolytic enzymes which are pumped out into the environment
• rot the material around
  them
• the fungus is suspended in its food source
• This means that they are SAPROPHYTES

Question 24

how do fungi reproduce?

Answer 24

• produce a large number of spores
• they are dispersed over large distances
• humans are constantly exposed to fungal spores

Question 25

how might fungi be classified?

Answer 25

• superficial
• subcutaneous
• systemic

Question 26

what fungal allergies are there?

and how might one get an allergy?

Answer 26

- inhalation of fungal spores might produce a wide range of allergies 
• Rhinitis
• Dermatitis
• Asthma
responses differ

Question 27

what are mycotoxins?

Answer 27

secondary metabolites of moulds that exert toxic effects on animals and humans

Question 28

what are symptoms of Mycotoxicoses?

Answer 28

- Breathing problems
• Dizziness
• Severe vomiting
• Diarrhoea
• Dehydration
• Hepatic and renal failure 6 days later

Question 29

what is the treatment for Mycotoxicoses?

Answer 29

Gastric Lavage - wash out the toxins

• Liver transplant

Question 30

what is candida?

Answer 30

candida is an example of superficial mycosis

Question 31

what is candida albicans?

Answer 31

opportunistic commensal

• present in GI
• when we are immunocompromised C. albicans can colonise and invade host tissues

Question 32

what are superficial candida infections?

Answer 32

• Usually due to impaired epithelial barrier function
• Most common in the new born and elderly

surfaces exposed and throat, vagina, bronchi and lungs