Fungal Infections Flashcards
What are fungi?
Eukaryotic living organisms divided into unicellular and multicellular. Only 12 species colonise humans
What are the features of fungi?
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
What is a spore?
One celled reproductive unit which can give rise to other units without sexual fusion
What is the feature of fungi plasma membrane?
Phospholipid bilayer stabilised by the molecule ergosterol, a steroid molecule that has an identical role to cholesterol in reducing fluidity
What is a hypha?
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
What are candida?
Spores that form via asexual reproduction from the tip of a hyphae in both unicellular and multicellular fungi.
What are the unicellular fungi?
Yeast and mould which reproduce by budding
What are the multicellular fungi?
Mushrooms and mould which reproduce by sexual reproduction.
What are saprocytes?
Organisms which feed on dead matter
How can fungi cause disease?
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.
What makes fungi unsuitable to disease in humans?
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
Which groups are most vulnerable to fungal infections?
Immunocompromised groups such as those with diabetes, pregnancy, taking steroids, chemotherapy due to being ubiquitous in the environment. Inhalation of fungi occurs everyday
What is an anamorph?
Asexual form of fungi
What is the asexual reproduction in fungi?
Nuclear fission occurs followed by either fragmentation, budding or spore formation
What is fungal fragmentation?
Mycelium separates into smaller components via mitosis and these individual components form new mycelium.
What is fungal budding?
Bulge forms on the side of the progenitor which divides by cytokinesis to then elongate and form new fungi
How do spores form?
Spores that are produced directly from the fungi are sporangium spores
Spores that are produced from the apical tip of the hyphae are condida
What is sexual reproduction in fungi?
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
What is homothallic?
Sexual reproduction between two identical mycelium
What is heterothallic?
Sexual reproduction between two different mycelium
What is yeast?
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
What is the pathogenic yeast?
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
What is candida albicans?
Opportunistic pathogenic yeast which can form both true and pseudohyphae
What is cryptococcus neoformans?
Round ovioid yeast cells transmitted from bird droppings and causes meningitis.
What is mould?
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
What is the pathogenic mould?
Aspergilius which can cause pneumonia.
What is a dimorphic fungi?
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
How can yeast and mould be differentiated
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.
What is mycoses?
Fungal infection
What is a superficial mycoses?
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
What is a cutaneous mycoses?
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
What is an example of a superficial mycoses?
Tinea versicolour
Dermatophytosis.
What is Tinea versicolour?
Tinea versicolour, a superficial myoces by Malasezzia fur fur which produces azelaic acid that produces bleaching/lightening effect of skin colour
What is dermatophytosis?
AKA ringworm, which is a superficial mycoses which uses keratin as a nutrient. There is NO itching and it occurs anywhere on the body.
What is subcutaneous mycoses?
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.
What is the most common deep mycoses?
Aspergillus which has an angiotrophic effect of invading blood vessels and causing pulmonary haemorrhage/infarction. This occurs in severely immunocompromised patients.
What is candiadis?
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.
What are the groups of dermatophysis?
Geophilic: contact with soil
Anthrophilic: contact with humans
Zoophilic: contact with animals
What are the classes of anti-fungals?
Amhpotecerin
Azoles
Echinocandins
How does amphotecerin work?
Bind to ergosterol and causes a pore to form which allows leakage of intracellular ions
How does azole work?
Inhibits lanosterol demythelase from lanosterol -> ergosterol. Causes depletion of ergosterol which inhibtis fungal growth. Examples include fluconazole.
How does echinocandins work?
Inhibits synthesis of glucan in the cell wall of fungi for systemic fungal infection in immunocompromised groups.
How is candida albicans identified?
Formation of true hyphae
What is a mycotoxin?
Toxin produced by a fungi. Can lead to ergotism where there is contamination of food with fungi which causes severe painful seizures
What is the most common deep mycoses?
Aspergillus fumatigus due to spore inhalation which is the most ubiqutous in the environment
