Virulence and pathogenicity- bacteria

Question 1

Capsule

(structure and function)

Answer 1

Capsule= polysaccharide outermost layer of bacterial cell

• allows cell to evade clearance
• protection from immune response and antibiotics
• protection from phagocytosis

Question 2

Discuss the toxins present in and on bacterial cell walls

Answer 2

Discuss the toxins present in and on bacterial cell walls

Gram-negative bacteria= thin peptid layer, between outer membrane and inner (plasma) membrane.

• Lipopolysaccharide (LPS)- amphophilic molecule in outer membrane. *** non-protenaceus

Gram-positive bacteria= thick peptid layer

• techoic acids

CELL WALL COMPONENTS CAUSE SEPTIC SHOCK

Question 3

Identify

Answer 3

LPS molecule

• head- Lipid A
• tail- polysaccharide

*** endotoxin

Question 4

Toxins

Answer 4

Toxins= invasion/host cell damage

• Proteinaceous toxins are exotoxins from gram-negtive bacteria.
• non-proteinaceous toxins are endotoxins are in cell wall?

Question 5

mechanisms of exotoxin delivery to host cells

Answer 5

Exotoxins can be delivered by…

• Secretion into surrounding environment
• Injection into cell via type 3 secretion systems

Mechanisms of Toxins…

• Enzymatic activity- binding and delivery of toxin
• Protyolytic break down of host proteins
• Membrane disruption- pore formation
• Toxins against IgA

Question 6

Adhesins

(structure/function)

Answer 6

Adhesins

Structure:

• Polypeptide (protein)
  
  • fimbrial (gram-neg)
  • afimbrial
• Polysaccharide

Function:

• expression of factors to allow bacteria to bind to host cell
• avoids removal by host mechanisms

Question 7

Invasins

(structure/function)

Answer 7

Invasins

Structure:

• extracellular- use enzymes that break down host allowing invasion. (ex. hemolysins)
• intracellular- whole organism enters host cell (phagocytosis)

Question 8

Understand ways in which intracellular pathogens survive in the host cell

Answer 8

Intracellular survival

• acidic phagolysosome
• phagosome with no fusion to a lysosome
• within cell cytosol
• lyse vacuole and then use host cytoskeleton to escape
• …none of this makes sense… ask ta.

Question 9

Describe the 2 methods of virulence regulation

Answer 9

Methods of virulence regulation

survival depends on ability to sense and respond to environment. bacteria rapidly adapt using two mechanisms to control expression of virulence genes.

**Sigma factors- protein subunits of RNA polymerases that control transcription

• sensor proteins- sense cell conditions
• response regulators- activate or repress transcription

Question 10

Describe the major ways in how bacteria evolve into novel pathogens (3)

Answer 10

Evolution of novel pathogens

• Horizontal gene transfer- molecular evolution of novel pathogens
• Donor to recipient- blocks of DNA contain large mobile genetic components
• Pathogenicity islands- contain virulence factors like adhesins, invasins and toxins

Question 11

Identify the major types of antibiotic resistance

Answer 11

Types of antibiotic resistance

• modification of antibiotic target sites
• alteration of antibiotic uptake
• inactivation of antibiotics
• can occur by deliberate gene transfer or spontaneous mutations