Bacterial and Fungal Pathogenesis

Question 1

summarize the important bacterial enzymes

Answer 1

Question 2

describe the 2 components of exotoxins and the 3 classes

Answer 2

Question 3

give examples of toxins and the producing organisms (tetanus toxin, pertussis toxin, TSST, pyrogenic exotoxins)

Answer 3

Question 4

describe the features (potency, used as vaccine, specificity of action, and how its released) associated with exotoxins vs endotoxins

Answer 4

Question 5

describe adhesion and colonization

Answer 5

• specialized adhesion structures (e.g. pili, fimbriae)
• 2 types of adhesion:
  
  • nonspecific
  • specific
• expression of adhesion structures = dependent on environmental conditions
• role: prevent removal
  
  • e.g. urinary tract: would be “flushed” out by urinary flow
• can involve specialized or non-specialized structures (e.g. capsule)

Question 6

describe tissue tropism and name 2 examples

Answer 6

Question 7

describe how a range of diffrerent bacterial surface structures can be used for adhesion

Answer 7

• external to cell wall/outer membrane
  
  • fimbirae/common pili
  • capsules & slime layer
• integral part of cell
  
  • teichoic and lipoteichoic acids
  • LPS
  • outer membrane proteins and porins
• adhesins: component on bacterial cell used for attachment to a tissue, cell or surface
• receptors: host cell molecule that the bacterial adhesin attaches to

Question 8

describe biofilm

Answer 8

• attachment to surface, replication and microbial production of sticky expolymeric substance (EPS) coating
• the default mode of growth
• estimated >70% of all human infxns including:
  
  • endocarditis, osteomyelitis, UTIs, STIs, pneumonia, peptic ulcers, etc.

Question 9

name 3 advantages of biofilm formation

Answer 9

1. better resistance to antimicrobial agents
2. resist host immune response
3. act as reservoir

Question 10

describe microbial acquisition of iron

Answer 10

Question 11

summarize the strategies for acquisition of iron by microorganisms

Answer 11

Question 12

describe evasion of microbes and intracellular survival & cell-cell spread

Answer 12

• intracellular phase for growth can be:
  
  • essential (obligate): e.g. Chlamydia trachomatis
  • at specific points (facultative): e.g. Salmonella
  • not necessary at all: e.g. Vibrio cholerae

Question 13

describe how microorganisms survive in phagocytic cells

Answer 13

• prevent fusion of phagosome and lysosome
• escape from phagolysosome
• resist/inactivate lysosomal enzymes
• enzymatically inactivate harmful oxygen species

Question 14

describe evasion via antigenic and phase variation

Answer 14

• antigenic variation = changes in pathogens’ recognizable surface antigens
• recognition and eradication more difficult
• also possible: phase variation (on/off)
• 2 levels:
  
  • genetic
    
    • recombination; mutation
  • epigenetic:
    
    • via DNA methylation

Question 15

describe the spread and dissemination of microorganisms

Answer 15

Question 16

give an example of an exotoxin

Answer 16