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MICB 3301 Exam 4 > Lecture 20 Mechanisms of Pathogenicity > Flashcards

Lecture 20 Mechanisms of Pathogenicity Flashcards

1
Q

What is a Virulence factor or Determinant?

A

Genetic, biochemical, structural features that contribute to virulence

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2
Q

Pathogenicity Islands

A

Large DNA regions that encode virulence factors

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3
Q

Describe “Viral Attachment” and name some examples

A
  • Capsid and envelope spike proteins mediate attachment
  • Ex
  • GP120 of HIV, binds CD4 and CCR5
  • Hemagglutinin of nfluenza binds sialic acid
  • SARS -CoV-2 binds ACE2
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4
Q

Viral Spread

A

-Viruses can spread via blood, neuronal or lymphatic systems

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5
Q

Tropism

A
  • cell, tissue, organ specificity

- determined by host cell receptor

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6
Q

How do viruses evade the “Innate Immune Response”?

A
  • Capsules - block complement opsonization and membrane attack complex
  • Proteases - degrade C3h (opsonin) or C5a (chemotactic factor)
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7
Q

How do viruses evade the “Adaptive Immune Response”?

A
  • block antigen processing, MHC export
  • Evade antibody -Antigenic Variation
    • Amino acid changes in virion spikes (common in RNA viruses)
  • Change cell surface outer membrane or pilli proteins

-Capsules - block antibody binding IgA proteases - enzymes that degrade IgA in secretions

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8
Q

What are some examples of Bacterial attachment

A
  • Streptococcus pneumoniae
  • Haemophilus influenzae
  • Neisseria meningitidis
  • Pseudomonas aeruginosa strains, called mucoid strains, make capsules
  • opportunistic pathogen in burn and cystic fibrosis patients.
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9
Q

Coagulase

A

Bacterial Virulence Determinant for Invasion - clots fibrinogen in plasma, clot protects pathogen.

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10
Q

Streptokinase

A

Bacterial Virulence Determinant for Invasion -activates plasmin, digests fibrin clots - pathogen moves from clotted area

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11
Q

IgA proteases

A

Bacterial Virulence Determinant for Invasion - destroy antibody

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12
Q

Hemolysins

A

Bacterial Virulence Determinant for Invasion - digest RBCs, releases iron

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13
Q

Siderophores

A

Bacterial Virulence Determinant for Invasion - released, bind iron

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14
Q

Dnase

A

Bacterial Virulence Determinant for Invasion - lowers viscosity of secretions, spread

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15
Q

Bacteremia

A

Bacterial Virulence Determinant for Invasion - spread can lead to the presence of bacteria in the bloodstream

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16
Q

Name the Intracellular Bacterial Pathogen described in lecture

A

Listeria monocytogenes

  • Gram +, food-borne pathogen
  • Produce, raw (unpasteurized) milk, cheese, deli meat
  • Psychrophile
  • Can cross placenta
  • Actin tail to move around inside the cell.
17
Q

Bacterial Intracellular Pathogens example

A
  • Chlamydia
  • Legionella
  • Mycobacterium tuberculosis
  • Salmonella
18
Q

Recall some examples of Bacteria evading innate and adaptive immunity by forming biofilms

A
  • Streptococcus pneumoniae - Otitis Media (infection of middle ear)
  • Pseudomonas in Cystic Fibrosis lung
  • Staphylococcus and Enterococcus on heart valves - endocarditis
  • Streptococcus mutans (and other bacteria) - dental plaque
19
Q

Membrane - Disrupting Exotoxins

A
  • Pore - forming exotoxins
    • Leukocidins
    • Hemolysins
20
Q

Superantigens

A

Protein released by pathogen

  • Cause T cells (>30%) to overexpress, release cystokines
  • Failure of multiple host organs

-Toxic Shock
Syndrome - cause by Staphylococcus aureus superantigen

21
Q

AB Extoxins

A
  • Two subunits
  • A - toxic effect
  • B - binds target cell receptor
  • Many AB toxins are ADP - ribosyltransferases
  • Remove ADP - ribose group from NAD and attach t to a host cell protein.
  • Host cell protein inactivated or functions abnormally
22
Q

Diphtheria toxin - Corynebacterium diphtheriae

A

Binds growth factor receptor

Enters by endocytosis

ADP - ribosyl transferase

Attaches ADP ribose from NAD onto EF - 2

23
Q

Host site specific AB toxins

A

Cholera toxin

  • Produced by Vibrio Cholerae
  • Enterotoxin
  • ADP - ribosyltransferase

Botulinum toxin
-Produced by Clostridium botulinum
-Neurotoxin
-

24
Q

Cholera Toxin

A
  • A subunit ADP - ribosylates host G protein
  • G protein activates Adenylarte Cylase enzyme
  • Increased cAMP activates Chloride Channel
  • Cystic Fibrosis Transmembrane Conductance Regulator
  • Chloride out
  • Sodium and water out
  • Profuse watery diarrhea

MICB 3301 Exam 4 (2 decks)

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