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Infectious Disease > Intro to Bacterial and Viral Pathogenesis > Flashcards

Intro to Bacterial and Viral Pathogenesis Flashcards

1
Q

This is the term for a microorganism that is capable of causing disease.

A

Pathogen

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2
Q

This is the term for clinical signs and symptoms of damage that occur as a result of host/pathogen interaction.

A

Disease

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3
Q

This is the term for persistence by multiplying on/within host.

A

Infection

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4
Q

T/F: Most microorganisms are beneficial and not pathogens.

A

True

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5
Q

What do most microorganisms do?

A
  • Protect against harmful organisms
  • Vitamins and nutrients
  • Digestion
  • Develop Immune System
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6
Q

Types of Microbes

A
  • Commensals
  • Opportunistic Pathogens
  • Primary Pathogens
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7
Q

This is a type of microbe that causes disease in a normal host. Survival is dependent on infection not necessarily causing disease.

A

Primary Pathogens

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8
Q

This is a type of microbe where disease is only present if there is a breach in defense. Such as MRSA.

A

Opportunistic Pathogens

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9
Q

This is a type of microbe that is constantly present and depends on humans for existence. In a normal host, there is no disease caused by this.

A

Commensals

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10
Q

What abilities do microbes have that can lead to infection?

A
  1. Breach host barriers and evade immune system
  2. Use biochemical tactics to replicate, spread, establish infection, and cause disease
  3. Transmit to new host
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11
Q

What can we do biologically to control and eliminate pathogens?

A

Use Innate and Adaptive Immune System

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12
Q

Stages of Bacterial Pathogenesis

A
  1. Entry
  2. Adherence
  3. Invasion of Tissues
  4. Avoiding the Immune System
  5. Virulence Factors
  6. Tissue Damage
  7. Transmission
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13
Q

Bacterial Pathogenesis Requirements for Entry

A
  • Must overcome host barriers
  • Compromise of barriers (skin cuts, burns, catheters, ports, sx appliances, IV drug use, smoking, insect bites, antacids, sex)
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14
Q

Common Sites of Entry

A
  • Mouth (ingestion)
  • Nose (inhalation)
  • Respiratory Tract (inhalation)
  • Eyes (contact/splash)
  • Ears (eustachian tube)
  • Urogenital (sex)
  • Anus
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15
Q

Bacterial Pathogenesis Requirements for Adherence

A
  • Attachment to cells
  • Receptor Binding
  • Pili are MAJOR adherence device (determines tissue specificity)
  • E. coli (UTI, P-pili, specific for urinary epithelium, helps prevent urine steam from removing bacteria)
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16
Q

Bacterial Pathogenesis Requirements for Invasion of Tissues

A
  • Invasion
    • Strep and Staph have specific enzymes to help gain entry to tissues
    • Collagenase and Hyaluronidase
  • Degrade through SQ tissues
  • Coagulase - accelerates the formation of a fibrin clot.
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17
Q

T/F: Walled off infection can be reached by immune system or abx

A

False, it cannot.

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18
Q

This is the term for bacteria that live inside eukaryotic cells and uses the sell as a protective factor from the immune system, utilizes endless supply of nutrients and ideal for replication.

A

Intracellular Survival

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19
Q

When a pathogens lives within an eukaryotic cell, what happens?

A
  1. Cause host cell cytoskeleton rearrangement and promotes uptake
  2. In Cytoplasm, it escapes phagosomes (enzyme based)
  3. Avoid acidification of phagosomes
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20
Q

Bacterial Pathogenesis Requirements for Avoiding the Immune System

A
  • Intracellular Lifestyle (antiphagocytic activity)
  • Blockage of signal transduction
  • Antigenic variation
  • Complement Resistance
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21
Q

Antiphagocytic Properties

A
  1. Protein A of S. aureus
    - Binds to IgG and phagocytes can’t bind.
  2. Polysaccharide Capsule
    - Anti-complement (inhibits complement deposition, strep)
  3. IgA Protease
    - Cleavage of IgA (Neisseria, Flu, Pneumonia)
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22
Q

Blockade of Cell Signaling

A
  • Introduce enzymes into phagocytic cells

For example: Yersina and Salmonella block signal transduction leading to phagocytosis and enzymes induce apoptosis

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23
Q

Antigenic Variation

A
  • Pili are major antigenic molecules

For example: N. gonorrhoeae causes endless array of pili. Over time they change pili and disguise it from the immune system.

24
Q

Complement Resistance

A
  • Ability to inhibit complement

For example: Salmonella possesses a Lipopolysaccharide inhibiting C5-9 complement and therefore prevents the lysis of the bacterium.

25
Q

Bacterial Pathogenesis Requirements for Avoiding the Immune System

A
  • Exotoxin

- Endotoxin

26
Q

Facts about Exotoxins

A
  • Produces by gram + and -

- Secreted directly by the microbe

27
Q

Exotoxin Proteins Examples:

Corynebacterium Diptheriae

A

Shuts down ribosomes and blocks protein synthesis leading to cell death

28
Q

Exotoxin Proteins Examples:

Vibrio Cholerae

A

Alters G-protein function and constitutive activation occurs. It increases cAMP and leads to watery diarrhea.

29
Q

Exotoxin Proteins Examples:

Clostridium Botulinium

A

Blocks release of acetyl choline from nerve terminal that leads to paralysis

30
Q

Exotoxin Proteins Examples:

Clostridium Tetani

A

Blocks the release of the inhibitory neurotransmitter glycine so excitatory neurons are unopposed.

31
Q

Facts about Endotoxins

A

Found only in Gram -
Component of Cell Membrane
Also known as LPS

32
Q

Effects of Endotoxins

A
  • Fever
  • Hypotension
  • DIC
  • Complement Activation
  • Activation of Macrophages

***Sepsis!

33
Q

T/F: TNF-alpha is an important plater in shock development.

A

True

34
Q

Bacterial Pathogenesis Requirements for Tissue Damage

A
  • Can be caused by the host (immune response)
  • Neutrophil and Macrophage
  • Proteases and Oxygen Radicals (Lung)
35
Q

Examples of Tissue Damage

A
  1. Post-Streptococcal Glomerulonephritis
    - - Immune complexes deposited in kidney
  2. Rheumatic Fever
    - - Cross reactivity of Streptococcal antibodies with heart valves
36
Q

Bacterial Pathogenesis Requirements for Transmission

A
  1. Bacteria cause illness to aid in transmission
    - - Cough to aid in air droplets
    - - Diarrhea to spread via fecal/oral route.
  2. Lethal disease is an accident
    - - If host dies, the bacteria loses home
    - - Most highly adopted bugs spare their host.
37
Q

Viral Structure

A
  1. DNA or RNA surrounded by a protein capsid
    - - Size ranges from 20 to 300nm
  2. Can be enveloped or non-enveloped
    - - Membrane coat derived from host cell
  3. Must overtake cell machinery to replicate
    - - Cannot make energy
    - - Cannot replicate or make proteins alone
  4. Have receptors on the capsid/envelope that allow them to attack specific cells
38
Q

Portals of Viral Entry

A
  • Respiratory Tract
  • GI Tract
  • Skin
  • Genitourinary
  • Blood
  • Trans-placental
39
Q

Viral Transmission

A
  1. Person to Person
  2. Mother to Offspring (vertical)
  3. Animal to Human – zoonotic infection
40
Q

Components of Viral Infection

A
  • Attachment
  • Entry
  • Uncoating
  • Replication
  • Assembly
  • Release
41
Q

Steps of Viral Replication

A
  1. Attachment
  2. Entry
  3. Uncoating
    4a. Transcription
    4b. Translation
    4c. Replication
  4. Assembly
  5. Release
42
Q

Components of Viral Infection:

Attachment

A

Specific proteins on surface of virus attach to specific molecules on the host cell surface. (Can be proteins or carbohydrates)

43
Q

Examples of Attachment:

Influenza

A

Sialic Acid on Host Cell

44
Q

Examples of Attachment:

EBV

A

CD3 Receptor on B-cells

45
Q

Components of Viral Infection:

Entry

A
  1. Non-enveloped
    - - Taken into cells by endocytosis
  2. Enveloped
    - - Fuse envelope with cell membrane
    - - Fusion of the viral membrane with the plasma membrane
    - - Releases the nucleocapsid directly into the cytoplasm
    - - Endocytosis of the viral particle - Release of the nucleocapsid into the cytoplasm
46
Q

Components of Viral Infection:

Uncoating

A
    • Nucleocapsid must be delivered to the site of replication within the cell
    • Most DNA viruses go to the nucleus
    • Most RNA viruses stay in cytoplasm
47
Q

Components of Viral Infection:

Replication

A
  • Must have synthesis of mRNA, protein, and copies of genome
  • DNA viruses use host cell DNA polymerase and RNA polymerase
  • RNA viruses stay in cytoplasm must either bring or produce a RNA polymerase to replicate and transcribe
  • Both types of virus use cell ribosomes for translation
48
Q

Components of Viral Infection:

Assembly

A
  • Viruses must assemble themselves
  • Interaction of proteins, membranes, and nucleic acids
  • DNA viruses usually assemble in the nucleus and RNA in the cytoplasm
  • Enveloped viruses acquire membrane from budding off the cell plasma membrane
49
Q

Components of Viral Infection:

Release

A
  • Can be done by lysis, budding, or exocytosis
  • Naked capsid are usually released by lysis
  • Enveloped are released by budding often without killing of the cell
50
Q

Viral Spread

A
  • Virus may replicate and remain at primary site
  • Some may disseminate to other tissues
    • Replicate in local tissues
51
Q

The term for when a virus is getting into the blood and travel to secondary sites of viral replication.

A

Primary Viremia

52
Q

The term for when a virus replicates at secondary site and gets in the blood again

A

Secondary Viremia

53
Q

Cell Damage

A
  • Most signs and symptoms of viral infection are due to cell death
    • Virally induced shut down of macromolecular synthesis (Shut down translation).
    • Induce apoptosis
    • Immune cytotoxic response (Cytotoxic T-cells kill infected cells)
54
Q

Evasion of Immune Response

A
  • Receptors for cytokines (IL-1 and TNF)
  • Viruses Block production of cytokines
  • Block the production of Interferon
  • Multiple antigenic type
55
Q

How viral infections persist?

A
  • Integration into DNA
  • Immune tolerance
    • Does not make antibodies
  • Antigenic variation
  • Spread cell to cell without extra-cellular component
  • Immunosuppression

Infectious Disease (6 decks)

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