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Pathology Summer 2020 > Fungi, parasites, prions > Flashcards

Fungi, parasites, prions Flashcards

1
Q

How are fungi similar to our cells?

A

Fungi are eukaryotes, have membrane bound organelles, they have DNA in chromosome form. This makes them hard to target and differentiate from our cells.

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2
Q

4 types of fungi and their characteristics

A

Yeast:

  • More virulent
  • Unicellular
  • Budding
  • Facultative anaerobes

Molds:

  • Less virulent
  • Multicelular
  • Sexual reproduction
  • Spore forming
  • Aerobic
  • Filamentous hyphae

Dimorphic (change back and forth between yeast and mold forms)

Sapryphytes: Live in decaying matter. Break down organic material.

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3
Q

How are fungal infections transmitted and what is the most commonly transmitted fungal type

A

Saprophytes are most commonly transmitted. By open wound inoculation or inhalation of spores.

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4
Q

Who is at risk for infection by fungal commensals

A

Old and young
Immunocompromised (AIDS, chemo, post transplant)
Diabetic

healthy individuals are usually able to fight off.

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5
Q

What makes fungi ubiquitous

A

They are able to adapt well to any host environment.

They have a wide range of temps
Can eat keratin
Low 02 requirements

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6
Q

Fungi and cytokine effects

A

They down regulate immune release of pro-inflam cytokines. Ex; TNF-a

They up regulate immune release of anti-inflam mediators.

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7
Q

3 ways that fungi can invade and evade

A
  1. Capable of morphological change. From avirulent (mold) to virulent (yeast) by changing gene expression.
  2. Survive phagocytosis
    - Capsule makes them slippery
    - Gliotoxin inhibits phagocytosis
    - Reproduce inside phagolysosome.
  3. Immunosuppressoin
    - Capsule blocks recognition by macrophages
    - Gliotoxin suppresses mast cell activation
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8
Q

Dual function of toxin released by fungi

A

Gliotoxin can inhibit phagocytosis and it suppress mast cell activation

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9
Q

Dual function of capsule on fungi

A

Can provide resistance to phagocytosis bc slippery and can block regognition from macrophages.

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10
Q

Key to clearance of many infections

A

Mast cell activation. Suppressed by gliotoxin of fungi

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11
Q

Fungi cellular damage by direct

A

Enzymes: proteases, phospholipase, elastase

Mycotoxins: Cause loss of muscle coordination, weight loss, tremors. Ex: aflatoxin aspergillus

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12
Q

Fungi cellular damage by indirect

A

Cell mediated immune response: collateral damage caused by t cells, MO, and neutrophils

Granuloma formation: due to not being able to break down fungi. can settle in lungs, nervous system or blood vessels.

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13
Q

Mycoses

A

Fungal infection in an animal

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14
Q

Three type of mycoses infections (broad)

A

Superficial/cutaneous
-Skin and hair

Subcutaneous
-usually due to penetrating trauma.

Systemic
-Inhalation or spores cause pulmonary or chronic granuloma

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15
Q

Type of fungi that causes cutaneous mycoses

A

Dermatophytes. Require keratin for metabolic process.

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16
Q

Dermatophytes

  1. transmission
  2. Mechanism of action
  3. 2 infections
A
  1. Person to person, animal to person, soil to person.
  2. Elicit host inflammatory response
  3. Pityriasis versicolor (patches on skin. Hypopigemented. Appear after UV exposure.)

And

Dermophytosis: Fungal infection of the skin. Lesion with central clearning. Ex: ringworm/tinea.

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17
Q

Where are these ring worm locations?

  1. Tinea capitis
  2. Barbae
  3. Pedis
  4. Curries
  5. Unguium
A
  1. Scalp
  2. Beard
  3. Foot
  4. Groin
  5. Nials
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18
Q

Commensal yeast

A

Candida albicans

Most common fungal infection in humans

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19
Q

Most common fungal infection in humans

A

Candida albicans. Commensal.

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20
Q

Where is candida albicans likely to cause infection

A

Mouth
Vagina
GI tract

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21
Q

Two types of infections caused by candida albicans (commensal)

A

Candidiasis (Thrush)
-Antibiotic treats

Candidosis

  • 30-40% mortality
  • spread throughout body. Infection.
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22
Q

Opportunistic fungi (4)

A

Aspergillus causes aspergillosis and aspergilomas in the lungs/inner ear/sinuses/eye.

Cryptococcus neoformans causes cryptococcosis in pulmonary. Causes meningitis and granulomas.

Pneumocystis jirovecii is an AIDs defining infection.

pneumocystis pneumonia. cough, fever, shortness of breath.

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23
Q

ASpergillus (opportunistic fungi)

A

Ubiquitous, Spore forming mold that causes aspergillosis in the lungs/inner ear/sinuses/eyes. Can cause aspergilloma- fungus ball that colonizes in a healed lung scar from previous disease.

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24
Q

Cryptococcus neoformans (opportunistic fungi)

A

Encapsulated yeast found in pigeon droppings.
Causes cryptococcosis that can be in the lungs and spread to CNS to cause meningitis or cutaneous granulomas.

Granulomas occur only in severely immunocompromised patients.

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25
Q

Pneumocystis jirovecii (opportunistic fungi)

A

Ubiquitous yeast.
AIDS defining infection.
Only in severely immunocompromised pts: maybe pt has Cancer or is taking a Chronic immunosuppressant medication

26
Q

Pneumocystis pneumonia (opportunistic fungi)

A

Cough, fever, rapid breathing, shortness of breath

27
Q

Primary pathogenic fungi

A

Infection may occur in healthy people.
Usually inhaled into lungs.
Histoplasmosis

28
Q

Histoplasmosis

A

Dimorphic
Found in ohio and mississippi river valleys. Soil and bird/bat feces.
Causes pulmonary granulomas. Travels to liver, heart, CNS, and eyes.

29
Q

How many people have positive skin test to histoplasmosis? (cell mediated immunity)

A

70%. Of those 70%, 4.4 people have ocular histoplasmosis.

30
Q

Characteristics of presumed ocular histoplasmosis

A
  1. Punched out lesions. “Histo spots.” most common
  2. Juxtapapillary atrophy. Atrophy around nerve
  3. Rare, but could have choroidal neovascularization. Most severe form.
  4. NO vitritis.
31
Q

Protozoa

  • cell type
  • 2 forms
  • Most common Protozoa infection in US
A

Unicellular eukaryotes
Trophozoite form and cyst form (really resistant to clearance)
Giardia lamblia is the most common- associated with fecally contaminated water. Long lasting diarrhea disorder.

32
Q

Helminths (3 types)

  • Cell type
  • How do you get it?
A

Nematodes, flukes, and tapeworms.
Multicellular eukaryotes
Fecally contaminated food/water. May be able to penetrate healthy skin.

33
Q

How do Protozoa and helminths invade and evade immune system?

A
  1. Prevent phagolysosome formation
  2. Change antigen surface proteins
  3. Coat themselves and host-antigens (fibrin) Helminths.
  4. IgA and IgG proteases
  5. Soluble antigen release. Diffuse immune response, not targets at infection.
  6. Inactivation of complement.
34
Q

How do Protozoa and helminths cause direct cellular damage?

A

Bulk properties- ability to reproduce and block lumen. Ex: bile duct, lymphatics

Toxins cause direct damage to tissues

35
Q

How do Protozoa and helminths cause indirect cellular damage?

A

Prolonged inflammatory response causes collateral damage

Granulomas

36
Q

How do Protozoa and helminths elicit a host immune response?

A

Cell mediated
ADCC
Eosinophils (helminths)

37
Q

Primary host of malaria

A

Humans

38
Q

What type of cell is malaria

A

Unicellular eukaryote. Protozoa.

39
Q

Malaria

  • What type of illness
  • How does it affect body?
  • How many species?
A

Mosquito borne
Hemolytic, febrile illness (increase in body temp)
-Cyclic chills. Certain time of day due to protozoa causing lysis of red blood cells= release intracellular contents= fever
-Fever
-Anemia bc lyses RBC
-Splenomegaly: Bc the spleen clears damaged RBCs

four main species.
Most common is plasmodium falciparum

40
Q

Events that cause malaria once bitten by mosquito

A

Protozoa are put into the body and reproduce in the liver and red blood cells. Causes RBC to lyse and makes them sticky. They may adhere to basement membranes and vessels to cause blocked lumen.

41
Q

Two examples of protozoa

A 
Malaria: Plasmodium falciparum 
Toxoplasma Gondii (cat is the final host) May cause toxoplasmosis
42
Q

Toxoplasma gondii

  • Final host
  • Sources?
  • Causes what
A

Protozoa infection with a complex life cycle. Final host is the cat.
Sources: undercooked meat, contaminated water, handling cat feces.
Toxoplasmosis: Most infections are asymptomatic, but can be fatal for fetus or immunocompromised. Can cross placenta and cause fetal encephalitis.

43
Q

Toxoplasmosis of the eye due to toxoplasma gondii

A

Caused by protozoa: toxoplasma gondii.
results in necrotizing retinitis due to immune system responding to infection. Causes vitritis, retinitis, and vasculitis (inflammation of vessels).

Looks like headlines in the fog.
Headlights bc it erodes retina and causes sclera to shine through (white)
Fog because the vitreous is cloudy due to immune cells.

usually unilateral.

44
Q

Toxocara Canis

A

Helminth (Nematode) infection
Dog is primary host
Human is dead end.

Can result in toxocariasis (ingestion of T canis eggs) or visceral larva migrans (worms in internal organs)

45
Q

Visceral larva migrans

A

Worms in internal organs due to toxocara canis infection (roundworm nematode helminth)

Abdominal pain 
HA 
weakness 
Fever
Coughing/asthma/pneumonia if in lungs
46
Q

Ocular larva migrans

A

Due to round worm/nematode/helminth in eye.
Usually found in macula due to increased blood flow there.

Vision loss can be severe
Usually unilateral

Clinical signs:

  • Uveitis
  • Vitritis
  • Neuroretinitis
  • Papillitis
  • Chronic endopathalmitis
  • **White, elevated granuloma of retina or optic disc.
47
Q

Oncocera volvulus

  • how is it transmitted?
  • What does it cause
A

Helminth transmitted only by black fly vector (cannot transmit human to human)

causes subcutaneous nodules (chronic pruritic dermatitis)
Onchocerciasis. Small worms moving through body to the eye (surface of cornea and anterior chamber). Chronic exposure without treatment causes inflammatory response and eventual scarring –> vision loss.

48
Q

2nd most common cause of infectious vision loss

A

Onchocerciasis (small worms moving to eye) from onchocerca volvulus.

Most common is chlamydia.

49
Q

Riverblindness.

A

Onchocerciasis. Parasitic disease caused by tiny worms, microfilariae. Transmitted by black fly.

50
Q

How to treat helminths

A

Interfere with their NT

Inhibit arachidonic and microtubule synthesis (problematic bc we use these. Side effects will occur)

51
Q

How to treat protozoals

A

Inhibit protein and RNA synthesis
Inhibit cell division
Disrupt generic material

52
Q

What are prions

A

Misformed proteins that are nonliving, but pathogenic and transmissible by person to person.

They cause infection and induce conformational changes in proteins. No DNA or RNA.

53
Q

Prion pathogenesis

A

Gradual.

  • Causes neuronal loss –> Expressive astrocytes.
  • Amyloid plaque formation. Accumulates and we can’t break down.
  • No immune response bc self molecule
54
Q

prion appearance in neural tissue

A

Sponge-like with amyloid plaques and astrocytosis

55
Q

Prion disease in animals

A

Bovine spongiform ecephalopathy- mad cow
Scrapie in sheep
Chronic wasting disease in deer
Can also affect squirrels and travel to humans via kentucky burgoo.

56
Q

3 types of prion diseases in humans

A
  1. Creutzfeldt Jakob disease (CJD)
  2. Variant CJD
  3. Kuru
57
Q

Creutzfeldt-Jakob disease

A

85% sporadic (random mutation)
5-10% inherited
Very rare

58
Q

Variant CJD

A

Transmitted by person to person by:

Human growth hormone
Contaminated surgical instruments (v hardly and can persist thru autoclaving)
Infected corneal graft
Consumption of infected tissue

59
Q

Kuru

A

Consumption of human CNS tissue. Culture in papua new guinea.

60
Q

Prion disease clinical manifestations

A 
Long incubation period (slow infection)
Loss of muscle coordination
Dementia- loss of cognitive function
Progressive insomnia 
NO signs of inflammation or fever
90% fatal in 1 year
61
Q

Prion disease diagnosis

A

Brain or tonsil biopsy- looking for amyloid plaque
Usually done after death as confirmatory
Blood test is under development

62
Q

Treatment of prion disease

A

There is none. Palliative.

Pathology Summer 2020 (19 decks)

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