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Block 1 - Week 5 > Introduction to Fungi and Parasites > Flashcards

Introduction to Fungi and Parasites Flashcards

1
Q

Are fungi Eukaryotic or Prokaryotic organisms?

What are the implications of this?

A
  • Eukaryotic organisms
  • Fungi and humans share many characteristics such as both having:
    • Nuclei
    • Similar mitochondria
    • Similar ribosomes
    • Similar folate pathways
  • This means that many anti-biotics won’t work on fungal infections
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2
Q

What are some unique characteristics of fungal cells that differentiate them from human cells?

A
  • Ergosterol in the cell membrane
    • This is the target of many anti-fungal drugs
  • Chitin
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3
Q

Yeast

A
  • Unicellular form of fungi (spherical/ellipsoid)
  • Reproduce via budding or fission
    • Mother cell pinches off to produce daughter cell
      • Form pseudohyphae: elongation of yeast cell budding (relatively short with no separation of cytoplasm)
  • Slightly smaller than RBCs
  • Indentified via microscopic morphology and biochemical tests
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4
Q

Mold

A
  • Multicellular form of fungi
  • Tubular structures known as hyphae (2 types):
    • Septate hyphae: crosss-wall between cells
    • Coenocytic hyphae: nonseparated/nonseptate cells
  • Reproduction occurs by formation of spores (some yeast can also produce spores)
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5
Q

Dimorphic fungi

A
  • Occurs in both yeast and myceilal/hyphal forms
    • Is a yeast at 37 degrees C (human body temperature)
    • Is a mold at 25 degrees C (room temperature)
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6
Q

Budding

A

Process of yeast replication

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7
Q

Pseudohyphae

A

Elongation of yeast cell buddding; relatively short with no separation of cytoplasm

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8
Q

Hyphae/Germ Tube

A

Growths of mold (growth from spore has no constriction)

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9
Q

Vegetative hyphae

A
  • Mold
  • Form seen in tissue
  • Grow on or beneath culture medium surface
  • Angels of hyphae are one of the few distinguishing features
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10
Q

Aerial hyphae

A
  • Mold
  • Usually only seen in culture
  • Contain structures for production of spores
  • Hyphae that project above the surface of the media
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11
Q

Septate hypha and Coenocytic hypha picture

A
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12
Q

What type of fungi can have capsules?

A

Yeast

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13
Q

Primary Pathogens

A

A pathogen that can infect healthy individuals

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14
Q

Opportunistic Pathogen

A

A pathogen that can only infect immunocompromised (innate or acquired) individuals

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15
Q

What type of immune response is activated in response to fungi?

(General)

A

Usually a TH17 response that involves are large influx of neutrophils

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16
Q

Parasite Reservoir

A

Source of parasites in the enviornment

17
Q

Parasite’s Definitive Host

A

Host in which sexual reproduction of the parasite takes place

This is where you will find mature adult parasites

18
Q

Parasite’s Intermediate Host

A

Host that harbors an asexual or larval stage of the parasite

19
Q

Parasite Vector

A
  • Agent capable of transmitting the pathogen from one host to another (ex. flies, ticks, mosquitos)
    • Mechanical Vector: Moves parasite from one organism to another
    • Biological Vector: Parasite develops in the vector
20
Q

Forms of Parasite Transmission

A
  • Injury
  • Ingestion
  • Inhalation
  • Person to person
  • Contact with contaminated water or soil
  • Transmission from vectors (ex. mosquitos)
  • Fomites (objects/materials that can carry infection)
21
Q

Do parasites have a cell wall?

A

No; parasites lack cell walls, and this can make them difficult to target.

22
Q

What are the two major types of parasites?

A
  • Protozoans: single celled organisms
  • Metazoans: multicellular organisms
    • Large worms called helminths
      • Platyhelminths (flatworms)
      • Nematodes (roundworms)
23
Q

Protozoans

A
  • Microscopic parasites
  • Single cell organisms: can be free living or intracellular
  • Morphologically diverse but biochemically similar to humans
24
Q

Protozoan Pathology

A
  • Pathology of infection is due to:
    • Malnutrition (The Protozoan absorb nutrients)
    • Blockage of systems
    • Release of toxic byproducts
  • Two main classes of infection:
    • Gastroenteritis (Ex. Giardia)
    • Systemic disease (Ex. Malaria)
25
Q

Protozoan Transmission

A
  • Ingestion
  • Inhalation
  • Mechanical vector
  • Athropod vector (Ex. Tse tse fly)
26
Q

Immune Response to Protozoan Infection

A
  • No single immunologic response is associated
  • GI an GU protozoan infections are self-limiting (results in clearance of the pathogen or death of the host)
  • Generally lack eosinophilia
27
Q

Protozoan Treatment

A
  • Often difficult to treat
  • Target mechanism of many anti-protozoan drugs is not well described
  • Some antibacterials work on certain protozoans
28
Q

Protozoan Life Cycle (Main Point/General Concept)

A

Main point = it’s complicated and it makes it difficult to treat

  • Protozoan life cycles can be complex
  • Can involve various hosts and vectors
  • Can involve sexual and asexual reproduction
29
Q

Helminths

A
  • Free living obligate parasites
  • Macroscopic and multicellular
  • Reproduce sexually
  • Each Helminth has a specific tissue tropism it prevers (Example: Liver, Lung, GI Tract, etc.)
30
Q

Helminths Pathologies

A
  • Local tissue damage
  • Blockage of necessary flow
  • Immunologic response
  • Malnutrtion d/t directly absorbing nutrients from host
    • Exception: Hookworms which ingest RBCs
31
Q

Types of Helminths (Picture/Diagram)

A
32
Q

Helminth Transmission

A
  • Ingestion
  • Inhalation/ingestion
  • Anthropod Vector
    • Biologic Vector (Ex. Black Fly)
    • Mechanical Vector (Ex. House Fly)
  • Direct infection (Ex. Hookworms burrow directly into skin)
33
Q

Helminth Diagnosis

A
  • Blood antigen or antibody tests
  • Direct observation of eggs or parasite in patient sample (Example: fecal sample)
    • Laboratory test on feces = OVA and Parasite Screen
34
Q

Helminth Life Cycle (General Concept)

A

Helminth life cycle can be very complex with various hosts/vectors

35
Q

Treatment of Helminth Infections

A

Helminth biochemistry is similar to humans which makes treatment difficult. Some treatments include:

  • Glutamate-gated chloride channel (Avermectins/Ivermectin)
  • Colchicine-sensitive site of B-tubulin (Bendazoles)
36
Q

Immune Response to Helminth Infection

A
  • Immune response to helminths is universally a TH2 response causing Eosinophilia
  • Eosinophils have been shown to kill helminths in vivo

Block 1 - Week 5 (10 decks)

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