Virulence and pathogenicity- bacteria Flashcards Preview

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Flashcards in Virulence and pathogenicity- bacteria Deck (11):
1

Capsule

(structure and function)

 

Capsule= polysaccharide outermost layer of bacterial cell

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

2

Discuss the toxins present in and on bacterial cell walls

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

3

Identify

Q image thumb

 

LPS molecule

  • head- Lipid A
  • tail- polysaccharide

*** endotoxin

A image thumb
4

Toxins

Toxins= invasion/host cell damage

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

5

mechanisms of exotoxin delivery to host cells 

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

A image thumb
6

Adhesins

(structure/function)

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

 

 

 

7

Invasins

(structure/function)

Invasins

Structure:

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

8

Understand ways in which intracellular pathogens survive in the host cell

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. 

9

Describe the 2 methods of virulence regulation

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

10

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

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

 

11

Identify the major types of antibiotic resistance

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