Fungal Infections Flashcards
What are the two main phyla of fungi?
Ascomycota
Basidiomycota
Which fungus out of the basidiomycetes causes the largest burden of disease?
Cryptococcus neoformans and Cryptococcus gatii
Cryptococcus neoformans Causes cryptococcal meningitis
What three types of illness do fungi cause?
Allergies
Mycotoxicoses
Mycoses
Define mycotoxicosis.
A toxic reaction to the ingestion/inhalation of toxins produced by fungi
What is known as the most carcinogenic natural compounds and what produces it?
Aflatoxin – Aspergillus flavus
causes liver damage from hep B, then predisposes to liver cancer
Define mycosis.
Disease caused by fungi that is classified based on the level of tissue affected
What are the four types of mycosis?
Superficial
Cutaneous
Subcutaneous
Systemic
What are superficial mycoses? Give some examples.
Mycoses that affect the skin and hair
No tissue is invaded so there is no cellular response
Black piedra
White piedra
Dandruff
Tinea nigra
What are cutaneous mycoses? Give some examples.
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
What are subcutaneous mycoses?
Chronic, localised infections of the skin and subcutaneous tissue following traumatic implantation of the aetiological agent.
What type of fungal infection is a big problem in transplant settings?
Aspegillosis
There is a very high mortality for systemic mycoses
What are the three types of candida infection that can occur in the immunocompromised?
Mucosal
Systemic
Superficial
What are the three types of mucocutaneous candidiasis that occurs in people with HIV?
Oesophageal
Vulvovaginal
Oropharyngeal
high mortaility rates once the disease is systemic
What are the main risk factors for systemic candida infections?
Chemotherapy
Gut-related surgery
Catheters
- not seen in healthy humans
What are the three main targets for antifungal therapy?
- Cell membrane - use ergosterol instead of cholesterol
- DNA synthesis
- Cell wall
How do antifungals that target the cell membrane work? Give some examples.
- Fungal cell membranes contain ergosterol instead of cholesterol
- Some antifungals inhibits ergosterol synthesis
Examples: azole this is the main drug group (itraconazole)= drug
How do antifungals that target DNA synthesis work? Give an example.
Pyrimidine analogues are used to interfere with DNA synthesis
Example: Flucytosine (used for Cryptococcus)
How do antifungals that target the cell wall work? Give an example.
- 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)
What components are found in fungal cell walls but not in mammalian cell walls?
Glucan
Chitin
what are general features of fungi?
- they are eukaryotes
- they have several chromosomes and a massive gene complex
what are most fungal infections?
- ascomycetes
where might the cyrptococci go?
- into the lungs although alveolar macrophages are good at destroying them
- if they get into the sugar rich brain then might cause meningitis
how do fungi digest their food?
- 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
how do fungi reproduce?
- produce a large number of spores
- they are dispersed over large distances
- humans are constantly exposed to fungal spores
