Block C Lecture 2: Fungal Pathogens Flashcards
What are the 3 categories of medical importance when dealing with diseases caused by fungi?
Mycotoxicases
Hypersensitivity Diseases
Host colonisation and resulting disease state
(Slide 4)
What are 3 examples of specialised metabolites that fungi produce?
Alkaloids
Toxins
Psychotropic Agents
(Slide 5)
What do mycotoxicoses result from?
Due to accidental or recreational ingestion of fungal toxins
(Slide 5)
How are mycotoxicoses treated?
Firstly by induced emesis (vomiting) followed by supportive therapy (assisted breathing / fluid)
(Slide 5)
What do ergot alkaloids result in?
Convulsions and gangrene (due to vasoconstriction)
(Slide 5)
What do aflatoxins cause?
Gross hemorrhage and necrosis of tissue in birds
(Slide 6)
How can aflatoxins affect humans?
As it can also affect the human food chain
(Slide 6)
What chemical property do aflatoxins have?
They are carcinogenic
(Slide 6)
What is fungal hypersensitivity caused by?
Host inhaling fungal antigen, then hypersensitivity arises as a result of immunoglobulin production + lymphocyte stimulation
(Slide 7)
What do fungal hypersensitivity diseases not require?
Fungal growth
(Slide 7)
What can be used to identify fungal hypersensitivity?
Skin tests
(Slide 7)
What are the 3 different types of mycoses?
Superficial
Subcutaneous
Systemic
(Slide 9)
What cell trait do many pathogenic fungi exhibit?
They are dimorphic (exist either as yeasts or in filamentous form)
(Slide 10)
Why is the morphology of spores important?
In identification and diagnosis of fungal diseases
(Slide 10)
What is superficial mycosis?
When the fungus only infects the surface layer of the skin, hair or nails
(Slide 11)
What can be used to treat superficial mycosis?
It is mostly treatable with topical antifungal creams or liquid aerosols
(Slide 11)
What are fungi capable of producing superficial mycoses collectively called?
Dermatophytes
(Slide 11)
What do Trichophyton Spp. cause?
Fungal infections of the feet and other moist skin surfaces
(Slide 11)
How are Trichophyton species transmitted?
By spores (via flaking and itching skin)
(Slide 11)
What is subcutaneous mycosis?
A fungal disease which infects the deeper layers of the skin
(Slide 12)
What 2 ways can subcutaneous mycosis be treated?
Mostly treatable with topical drugs and azole antifungal agents are also often used to treat it
(Slide 12)
What fungi causes sporotrichosis?
Sporothrix schenckii
(Slide 12)
What is sporotrichosis?
An occupational hazard of anyone who works in close contact with soil agriculture, as spores can enter through cut skin
(Slide 12)
What is chromoblastomycosis?
Causes formation of crusty, wart-like lesions on the hands / legs and can be caused by fungal infection via puncture wound
(Slide 12)
What is systemic mycosis?
When fungal growth infects the internal organs
(Slide 13)
Where do systemic fungal pathogens normally live?
In soil
(Slide 13)
How do systemic fungal pathogens infect humans?
Due to inhalation of airborne spores, with the infection then travelling from the lungs to the other organs and the skin
(Slide 13)
Why is chemotherapy of systemic mycosis difficult?
Because of issues with toxicity
(Slide 13)
What 2 groups do systemic fungal pathogens generally infect?
The elderly or otherwise immunocomprimised individuals (such as AIDS patients)
(Slide 13)
What is the difference between primary and secondary mycosis?
Primary mycosis is when an healthy individual is infected whereas secondary mycosis is when an individual with a predisposing condition is infected
(Slide 13)
What is histoplasmosis?
When inhaled spores from histoplasma capsulatum germinate and grow in the lung
(Slide 14)
What does Coccidioides immitis cause?
Coccidioidomycosis
(Slide 15)
What symptoms does coccidioidomycosis exhibit?
Respiratory symptoms
(Slide 15)
What can coccidioidomycosis eventually lead to?
Pneumonia
(Slide 15)
What fungi causes blastomycosis?
Blastomyces dermatitidis
(Slide 16)
Where does blastomyces dermatitidis live?
In rotten wood and soil near bodies of water
(Slide 16)
What is blastomycosis?
A lung infections that can lead to skin lesions if untreated
(Slide 16)
What does paracoccidioides brasiliensis cause?
Paracoccidioidomycosis
(Slide 17)
What is paracoccidioidomycosis?
A initially pulmonary fungal infection that can lead to lesions forming on the face or other extremities (such as the limbs)
(Slide 17)
How can paracoccidioidomycosis be treated?
With azole antifungal agents
(Slide 17)
What does Cryptococcus neoformans cause?
Cryptococcosis
(Slide 18)
Where can cryptococcosis occur?
In almost any organ in the body
(Slide 18)
Where does cryptococcosis first infect?
Either the lungs or a wound
(Slide 18)
What kind of people does cryptococcosis infect?
HIV/AIDS patients (immunocompromised individuals)
(Slide 18)
What can candida albicans be a minor component of?
Normal human flora
(Slide 20)
What severity are infections caused by candida albicans?
Can be mild (such as thrush) to severe in individuals who are immunocompromised
(Slide 20)
What method does candida albicans use to generate genetic diveristy?
Chromosomal rearrangements
(Slide 20)
Why are biofilms a problem in medical settings?
As they are difficult to treat with antifungal agents
(Slide 20)
What fungi is pneomocytosis pneumonia often caused by?
Pnemocytosis jirovecil
(Slide 21)
What are 3 examples of people which pneomocytosis can infect?
People undergoing chemotherapy
People with AIDS
Premature / severely malnourished children
Elderly people
Infants with hyper IgM syndrome or an X-linked or autosomal recessive trait
(Slide 21)
Why are fungal infections difficult to treat in eukaryotes?
As fungi share alot of cellular machinery with animals and humans and few drugs target metabolic processes that are unique to fungi
(Slide 22)
What is ergosterol?
An analogue of cholesterol found in fungal plasma membranes
(Slide 23)
What are the 2 main classes of ergosterol inhibitors?
Polyenes and Azoles
(Slide 23)
What is the mechanism of action of azoles and polyenes?
They bind to ergosterol, deplete it in the membrane and then toxic intermediates accumulate resulting in the destabilisation of fungal cell membranes, leading to cell death
(Slide 23)
What is the mechanism of action of echinocandins?
The inhibit the synthesis of glucan in the cell wall via the inhibition of the enzyme 1,3-ß glucan synthase.
(Slide 24)
What are ß glucans?
Carbohydrate polymers that are cross-linked with other fungal cell wall components
(Slide 24)
What does the inhibition of ß-glucans prevent?
Fungal cell wall synthesis
(Slide 24)
What are DNA synthesis inhibitors?
They are nucleic acid analogues which inhibit enzymes required for DNA synthesis
(Slide 25)
What infections are DNA synthesis inhibitors used to treat?
Candida infections and Cryptococcus neoformans
(Slide 25)
