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Immunology (M1) > Microbial Pathogenesis and Mechanisms of Virulence > Flashcards

Microbial Pathogenesis and Mechanisms of Virulence Flashcards

1
Q

Pathogenicity

A

An organism’s ability to cause disease

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2
Q

Pathogenesis

A

A process resulting in disease

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3
Q

Pathogen

A

organism that can cause disease

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4
Q

Virulence

A

Degree of damage or disease resulting from infection

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5
Q

Infectivity

A

Likelihood of causing infection and/or disease with exposure to a particular dose

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6
Q

Three factors influencing infectious disease outcomes

A
  1. Susceptible host
  2. Conducive Environment
  3. Pathogen
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7
Q

Rhinovirus vs. Influenza vs. Ebola

A

Rhinovirus: High infectivity, low virulence
Influenza: moderate infectivity, greater virulence
Ebola: high both

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8
Q

Spectrum of relationships between microbes and hosts

A
  1. Essential/mutually beneficial
  2. Colonization
  3. Infection/disease (active vs latent)
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9
Q

Acquisition/Transmission of Microbial Agents

A

Endogenous vs. exogeneous

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10
Q

Endogenous transmission

A

Organism escapes from location where it is part of the normal microbiome

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11
Q

Exogenous transmission

A
  1. Person to person (communicable)
  2. Animal to person (zoonoses)
  3. Insect to person (vector borne)
  4. Environmental
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12
Q

Routes of transmission

A
  1. Epithelial surfaces

2. Deep tissue penetration

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13
Q

Conceptual framework for infectious diseases

A
  1. Encounter
  2. Entry
  3. Spread
  4. Multiplication
  5. Damage
  6. Outcome
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14
Q

Three categories for microbial virulence factors

A
  1. Structures involved in attachment, adherence, and invasion
  2. Toxins involved in cell or tissue damage
  3. Processes involved in immune avoidance
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15
Q

Bacterial pili

A

Filamentous structures extending from the bacterial surface; Allow adherence to host cells/matrix

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16
Q

Type IV pili

A

Extend, bind, and retract

Promote surface motility, microcolony & biofilm formation,, adherence to host cell, and immune evasion

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17
Q

Pili vs Flagella

A

Both filamentous appendages

Pili shorter, thinner, more numerous; may be polar or peritrichous; primary function attachment (vs. locomotion)

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18
Q

Specialized bacterial secretion systems

A

Gram- bacteria can use type III, IV and V systems to inject substrates (virulence factors: toxins or receptors) into other cells

19
Q

Bacterial nanomachines

A

T3SS

20
Q

E. coli infection strategy

A
  1. Bundle forming pili: initial attachment
  2. T3SS injects Tir protein (bacterial receptor) which binds to Intimin (bacterial adhesion)
  3. Hijacks host actin filaments
  4. Forms pedestal
21
Q

Viral attachment

A

Mediated by surface proteins of virion:
Naked viruses = capsid proteins (enters via endocytosis)
Enveloped = glycoprotein spikes (enters via membrane fusion or endocytosis)

22
Q

HIV viral attachment

A

GP120 (binds to CD4 on T-cell) –> conformational change to allow GP41 binding –> initiates viral envelope fusion

23
Q

Endotoxins

A

Lipopolysaccharide or Lipooligosaccharide (LPS and LOS)

Integral part of gram - bacterial outer membrane - Lipid A = toxic –> stimulator of innate immune responses

24
Q

How are serotypes defined?

A

O-antigens

25
Q

Pathogen-Associated Molecular Patterns (PAMPS)

A

Microbial molecules recognized by Pattern Recognition Receptors of the innate immune system

26
Q

Bacterial PAMPS engage ___ TLRs

A

extracellular

27
Q

Viral (and bacterial) PAMPS engage ____ TLRs

A

intracellular

28
Q

Exotoxins

A

Secreted toxins produced by Gram+ and Gram- bacteria; frequently encoded on plasmids or bacteriophage

29
Q

Toxin classifications

A
  1. Based on structure/function (A+B, Pore-forming, and Superantigen toxins)
  2. Based on site of action (enterotoxins, neurotoxins, tissue invasive toxins)
30
Q

A+B toxins

A

Active + Binding, variations on theme (Cholera toxin A + 5B, Anthrax toxin 2A + B)

31
Q

A+B toxin-mediated diseases

A
  1. Diphtheria
  2. Tatanus
  3. Pertussis
32
Q

DTaP Toxoid-based vaccines

A

Inactivated toxins, still immunogenic; vaccination can protect from toxin-mediated diseases

33
Q

Pre-forming toxins

A

S. aureus;

Secretion, binding, oligomerization, insertion (of pore)

34
Q

Superantigens

A

Nonspecific, stimulate massive polyclonal expansion of T-cells –> cytokine storm;
Staphylococcal and Streptococcal
Toxic Shock toxins

35
Q

Immune avoidance by microbial pathogens: structures

A
  1. Bacterial and fungal polysaccharide capsules
  2. Antigens that induce blocking antibodies
  3. Molecules that inactivate antibodies
  4. Molecules that mimic host structure
36
Q

Immune avoidance by microbial pathogens: Processes

A
  1. Antigenic variation
  2. Avoiding immune surveillance
  3. Suppressing immune responses
37
Q

Polysaccharide capsules

A

Extracellular, but attached to Gram-positive or Gram-negative bacterial surface

Define serotypes of pathogen

38
Q

Polysaccharide capsules avoid… (2)

A
  1. Phagocytosis

2. Immune recognition (complement and Ab)

39
Q

Common feature of pathogens that can disseminate via bloodstream to CNS

A

Polysaccharide capsules

40
Q

Neisseria meningitidis immune avoidance

A
  1. Antibodies don’t protect and block binding to other targets
  2. polysaccharide capsule mimics human antigens
  3. Produces IgA protease that cleaves IgA
41
Q

Antigenic variation

A

During infection, pathogens express different versions of key antigens

42
Q

Avoiding immune surveillance

A
  1. Biofilms
  2. Granulomas (wall off bacteria)
  3. Latency
  4. Expression of few surface proteins
43
Q

Suppressing/subverting immune responses

A
  1. HIV: destroys CD4+ cells –> immunodeficiency
  2. M. tuberculousis: prevents fusion of phagosomes & lysosomes in macrophages
  3. Staphylococcal Protein A binds IgG by the Fc recion

Immunology (M1) (11 decks)

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