LG 5.9 - Virulence Factors

Question 1

Definition of virulence?

Answer 1

• Extent of pathogenicity.

Question 2

What is the outcome of infection dependent upon?

Answer 2

• integrity of host defenses + # microorganisms + virulence of microorganism.

Question 3

Where are the virulence genes?

Answer 3

• Chromosome: pathogenicity islands - unique region exclusively associated with virulence, complete package required for delivery of pathogenic trait.
• Plasmids (can still have pathogenicity islands)
• Bacteriophages

Question 4

(4) How do bacteria evade host defenses?

Answer 4

• Invade cells: facultative intracellular vs. obligate intracellular.
• Make a capsule: interfere with complement deposition/ phagocyte engulfment (streptococcus pneumonia).
• Phase variation (changing surface molecules): Neisseria gonorrhoeae
• Antigenic variation (same bacteria)
• IgA1 protease (mucosal pathogens)
• Biofilms

Question 5

(4) Antibiotic resistance can happen by?

Answer 5

• Innate
• Acquired: mutation, gene exchange.
• Biofilms