Mycology (Fungus) - Lecture 4 Flashcards
Describe a fungal infection Eukaryotic or prokaryotic unicellular or multicellular Cell wall contents Reproducion
Eukaryotic, unicellular or multicellular
Multimorphic sturctures and stages
Cell wall contains chitin, ergosterol
Complex life cycles, sexual and asexual reproduction
What are four morphological stages of fungal infections?
1) Yeast or yeast-like stages
2) Pseudohyphae stages
3) Hyphae stages
4) Spores and spore-like stages
Describe the yeast or yeast-like stages
Sexual stages (conjugation) and asexual (budding) stages of reproduction Unicellulare, compromise mold
Describe pseudohyphae stages
Multicellular structures produced by incomplete budding
Describe hyphae stages
Multicellular structures, intricate connections and communication between cells
Long, filamentous, comprises mycelium
Describe spores and spore-like stages
Metabolically dormant, survive harsh environmental conditions, can travel through air
Unicellular structures
What are the four types of mycoses?
give examples of each
1) Superficial/cutaneous - Tinea
2) Subcutaneous - Sporothrichosis
3) Systemic - Blastomycosis, Histomycosis
4) Opportunistic - Candidiasis, Cryptococcosis, Pneumocystosis
Describe superficial/cutaneous mycoses
Fungal infection of the outermost layers of skin, hair and nails
Superficial - occur OUTSIDE the body
Cutaneous - occur IN the outer layers of the skin
Tinea = ringworm - infection due to fungus (NOT parasite)
Describe tinea capitis
What causes it?
Scalp ringworm
Fungal infection of the head and scalp - patches of hair loss, inflammation, itching, scaling, dandruf
Trichophyton and Microsporum cause it most commonly
Describe subcutatneous mycoses
Chronic, localized infection of the skin and tissue
may affect lymphatic system
May invade extradermal tissues
Describe sporotrichosis (Sporothrix schenkii)
Aka: Rose gardener’s disease
Affects the skin and lymph nodes
Causes nodular leasions at the point of entry and along lymphatic vessels
Can spread to joints, lung, bone
Describe systemic mycoses
Pass through the bloodstream
Primary systemic mycoses generally originate in the lung, and undergo hematogenous spread to other organs
What are systemic mycoses casused by?
Caused by dimorphic fungal pathogens - assume different morphologies at different body temperatures
- Mycelial at room temperature
- Yeast-like (spore) at body temperature
Give four examples of systemic fungal human pathogens
Blastomyces dermatiditis
Coccidioides immitis
Histoplasma capsulatum
Paracoccidioides brasiliensis
Who is more likely to get opportunistic mycoses?
Associated with immunosuppressed patients
- HIV-positive patients (AIDS-defining illness)
- Transplant recipients
- Elderly
- Premature babies
Give three examples of opportunistic mycoses
Candida albicans
Pneumocystis jiroveci
Cryptococcus neoformans
What is candida albicans? (candidiasis)
Thrush, ‘yeast infection’
Commensal organism of the skin
Describe oral candidiasis
Thrush
Associated with transplant patients, HIV-positive patients, cancer patients
White patches/plaques on the tongue, difficulty swallowing
Describe vulvo-vaginal candidiasis
‘yeast infection’
Pruritis, thick discharge, dysuria
What are some other forms of candidiasis?
Esophageal, Urinary tract, Penile (Candida balantidis), GI, Renal. Systemic, Disseminated
What is pneumocystis jiroveci? (pneumocystosis)
Commensal organism of the lung
Describe pneumocystosis (symptoms)
Fever, chills, non-productive cough, difficulty breathing, tachypnea, tachycardia
Extra-pulmonary complications: CNS, bone marrow, eyes, GI tract (rare)
What are prions?
Infectious proteins
Describe a prion infection
Transmitted by transferring a misfolded protein state
Presence of a misfolded protein stimulates the misfolding of normal proteins, disrupting their function
Prion disease cause transmissible spongiform encephalopathy
Who is Tikvah Alper/what importance with regards to prions?
In the 1960s he discovered infectious cause of scrapie, a disease in sheep, was resistant to ionizing radiation
Who is John Stanley Griffith/what importance with regards to prions?
In the 1960s he showed mathematical modelling suggests that scrapie is caused by a misfolded protein, which propagates by self-association
Who is Stanley Prusiner/what importance with regards to prions?
In 1980s he demonstrated that agents that cause transmissible spongiform encephalopathy are resistant to all methods used to destroy nuceic acid, but are sensitive to all methods used to destroy protein
Coined the term prion (proteinaceous infectious particle)
NOBEL PRIZE 1997
Describe:
PrP
PrPc
PrPsc
PrP - normal cellular protein localized on the surface of healthy nerve cells
PrPc - (cellular) normal form found in animals, and is subject to degredation by cellular proteases
PrPsc - (scrapie) mifolded form (prion form), and is resistant to degradation by proteases
What does PrPsc lead to?
Leads to accumulation of protein in the brain, followed by lesions (spongioform)
Name the prion disease in:
1) Sheep and farm animals
2) Cattle
3) Humans
1) Scrapie
2) Mad cow disease, bovine spongioform encephalopathy (BSE) variant CJD
3) Creuztfel-Jakob Disease (CJD), vCJD, Kuru
In humans describe the transmission of different CJD
Congenital - 5-10% of cases
Spontaneous - >85% of cases
Aquired - infection during medical procedures <1% of cases
What is vCJD and how is it transmitted?
It is an acquired disease, transmitted by consumption of contaminated products
Who is affected by Kuru?
Endemic to the Fore tribe of Papua New Guinea
Incidences of Kuru more common in women than men
What are clinical features of prion disease in humans?
Protein aggregation, amyloid plaque formation
Spongioform change, necrosis and leasions
Neuronal loss, astrocytosis
Poor muscle coordination, memory loss, dementia, coma
What are developing treatment strategies for prion disease in humans?
Decrease the presence of normal cellular protein (RNAi)
Passive/Active immunization strategies
