Mycology (Fungus) - Lecture 4

Question 1

Describe a fungal infection
Eukaryotic or prokaryotic
unicellular or multicellular
Cell wall contents
Reproducion

Answer 1

Eukaryotic, unicellular or multicellular
Multimorphic sturctures and stages
Cell wall contains chitin, ergosterol
Complex life cycles, sexual and asexual reproduction

Question 2

What are four morphological stages of fungal infections?

Answer 2

1) Yeast or yeast-like stages
2) Pseudohyphae stages
3) Hyphae stages
4) Spores and spore-like stages

Question 3

Describe the yeast or yeast-like stages

Answer 3

Sexual stages (conjugation) and asexual (budding) stages of reproduction
Unicellulare, compromise mold

Question 4

Describe pseudohyphae stages

Answer 4

Multicellular structures produced by incomplete budding

Question 5

Describe hyphae stages

Answer 5

Multicellular structures, intricate connections and communication between cells
Long, filamentous, comprises mycelium

Question 6

Describe spores and spore-like stages

Answer 6

Metabolically dormant, survive harsh environmental conditions, can travel through air
Unicellular structures

Question 7

What are the four types of mycoses?

give examples of each

Answer 7

1) Superficial/cutaneous - Tinea
2) Subcutaneous - Sporothrichosis
3) Systemic - Blastomycosis, Histomycosis
4) Opportunistic - Candidiasis, Cryptococcosis, Pneumocystosis

Question 8

Describe superficial/cutaneous mycoses

Answer 8

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)

Question 9

Describe tinea capitis

What causes it?

Answer 9

Scalp ringworm
Fungal infection of the head and scalp - patches of hair loss, inflammation, itching, scaling, dandruf

Trichophyton and Microsporum cause it most commonly

Question 10

Describe subcutatneous mycoses

Answer 10

Chronic, localized infection of the skin and tissue
may affect lymphatic system
May invade extradermal tissues

Question 11

Describe sporotrichosis (Sporothrix schenkii)

Answer 11

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

Question 12

Describe systemic mycoses

Answer 12

Pass through the bloodstream

Primary systemic mycoses generally originate in the lung, and undergo hematogenous spread to other organs

Question 13

What are systemic mycoses casused by?

Answer 13

Caused by dimorphic fungal pathogens - assume different morphologies at different body temperatures

• Mycelial at room temperature
• Yeast-like (spore) at body temperature

Question 14

Give four examples of systemic fungal human pathogens

Answer 14

Blastomyces dermatiditis
Coccidioides immitis
Histoplasma capsulatum
Paracoccidioides brasiliensis

Question 15

Who is more likely to get opportunistic mycoses?

Answer 15

Associated with immunosuppressed patients

• HIV-positive patients (AIDS-defining illness)
• Transplant recipients
• Elderly
• Premature babies

Question 16

Give three examples of opportunistic mycoses

Answer 16

Candida albicans
Pneumocystis jiroveci
Cryptococcus neoformans

Question 17

What is candida albicans? (candidiasis)

Answer 17

Thrush, ‘yeast infection’

Commensal organism of the skin

Question 18

Describe oral candidiasis

Answer 18

Thrush
Associated with transplant patients, HIV-positive patients, cancer patients
White patches/plaques on the tongue, difficulty swallowing

Question 19

Describe vulvo-vaginal candidiasis

Answer 19

‘yeast infection’

Pruritis, thick discharge, dysuria

Question 20

What are some other forms of candidiasis?

Answer 20

Esophageal, Urinary tract, Penile (Candida balantidis), GI, Renal. Systemic, Disseminated

Question 21

What is pneumocystis jiroveci? (pneumocystosis)

Answer 21

Commensal organism of the lung

Question 22

Describe pneumocystosis (symptoms)

Answer 22

Fever, chills, non-productive cough, difficulty breathing, tachypnea, tachycardia
Extra-pulmonary complications: CNS, bone marrow, eyes, GI tract (rare)

Question 23

What are prions?

Answer 23

Infectious proteins

Question 24

Describe a prion infection

Answer 24

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

Question 25

Who is Tikvah Alper/what importance with regards to prions?

Answer 25

In the 1960s he discovered infectious cause of scrapie, a disease in sheep, was resistant to ionizing radiation

Question 26

Who is John Stanley Griffith/what importance with regards to prions?

Answer 26

In the 1960s he showed mathematical modelling suggests that scrapie is caused by a misfolded protein, which propagates by self-association

Question 27

Who is Stanley Prusiner/what importance with regards to prions?

Answer 27

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

Question 28

Describe: PrP PrPc PrPsc

Answer 28

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

Question 29

What does PrPsc lead to?

Answer 29

Leads to accumulation of protein in the brain, followed by lesions (spongioform)

Question 30

Name the prion disease in: 1) Sheep and farm animals 2) Cattle 3) Humans

Answer 30

1) Scrapie 2) Mad cow disease, bovine spongioform encephalopathy (BSE) variant CJD 3) Creuztfel-Jakob Disease (CJD), vCJD, Kuru

Question 31

In humans describe the transmission of different CJD

Answer 31

Congenital - 5-10% of cases Spontaneous - >85% of cases Aquired - infection during medical procedures <1% of cases

Question 32

What is vCJD and how is it transmitted?

Answer 32

It is an acquired disease, transmitted by consumption of contaminated products

Question 33

Who is affected by Kuru?

Answer 33

Endemic to the Fore tribe of Papua New Guinea | Incidences of Kuru more common in women than men

Question 34

What are clinical features of prion disease in humans?

Answer 34

Protein aggregation, amyloid plaque formation Spongioform change, necrosis and leasions Neuronal loss, astrocytosis Poor muscle coordination, memory loss, dementia, coma

Question 35

What are developing treatment strategies for prion disease in humans?

Answer 35

Decrease the presence of normal cellular protein (RNAi) | Passive/Active immunization strategies