09-10 Host-bacteria interactions & Infectious Disease

Question 1

Pathogenicity is determined by the ability of an organism to…

Answer 1

Colonise underlying tissue

Question 2

4 Stages of infection…

Answer 2

1) Entry
2) Adherance
3) Invasion
4) Growth

Question 3

Biofilms can be made up of…

Answer 3

Single or multiple species

Question 4

Which ‘ability’ of bacteria facilitates the Entry phase?

Answer 4

Motility (e.g. flagella)

Question 5

Which feature of bacterial cells facilitates adhesion (e.g. to skin or mucosa)?

Answer 5

Sticky capsule, fimbriae

Question 6

Bacteria that form biofilms may vary on a spectrum between two forms, known as…

Answer 6

• Motile (corresponing to planktonic (individual) living)
• Sessile (corresponding to community living)

Question 7

Describe a change in features that may be seen between the motile and sessile forms of a bacterium…

Answer 7

Flagella in the motile form and fimbriae and capsule in the sessile form

Question 8

Bacterial capsules are made from…

Answer 8

Polysaccharides

Question 9

Name two functions of bacterial capsules…

Answer 9

• Can hide antigens from host immune system
• Can cause damage (for example blocking xylem in plants)

Question 10

Xantham gum is an example of an industry use of…

Answer 10

Bacterial capsules

Question 11

Describe the production of the fimbrial pilus (3)…

Answer 11

• Secretion by Sec machinery
• Crosses periplasmic space via chaperone protein
• Crosses outer membrane via usher protein

Question 12

Lectin-like protein with sticky ends responsible for the adhesive properties of fimbriae

Answer 12

FimH

Question 13

Describe how fibriae respond to shear forces…

Answer 13

• Fast flow or high shearing forces causes fimbriae to attach more firmly
• Low flow causes fimbriae to detatch

Question 14

Protein secretion in bacteria depends on structure (gram positive vs gram negative).

Give some examples of proteins secreted by bacteria…

Answer 14

• Harmolysin
• Flagella subunits
• Firmbrial subunits
• Toxins
• Enzymes
• Proteinacious S-layers

Question 15

Describe the two main pathways of bacterial protein secretion…

Answer 15

• SEC (for unfolded proteins)
• TAT (for unfolded proteins)

Question 16

Protein secretion machines are designated by the nomenclature…

Answer 16

Type x secretion system (e.g. Type II secretion system)

Question 17

Measuring pathogenicity and virulence

Pathogenicity can be measured by presence of a Pathogenicity Factor. This is the…

Answer 17

Feature enables pathogenicity

(the gene that codes for the part of bacteria that causes disease in the host)

Question 18

Measuring pathogenicity and virulence

Virulence factors are…

Answer 18

Molecules which enable a microorganism to effectively colonise the host

Question 19

Horizontal gene transfer contributes to the evolution of pathogenicity factors. This process is often assisted by…

Answer 19

Bacteriophages

Question 20

Bacterial toxins may be divided into two types…

Answer 20

Endotoxins and exotoxins

Question 21

Exotoxins have ( higher / lower ) toxicity than endotoxins…

Answer 21

Higher

Question 22

Cytolytic exotoxins cause…

Answer 22

Cell lysis

Question 23

Exotoxins are…

a) secreted by bacteria into host
b) released when the bacterial cell is lysed
c) specific to gram-negative bacteria

Answer 23

Exotoxins are…

a) secreted by bacteria into host

b) released when the bacterial cell is lysed
c) specific to gram-negative bacteria

(B and C are true of endotoxins)

Question 24

AB exotoxins are made up of two subunits, A & B. What are their functions?

Answer 24

B binds to specific receptors, which facilitates the uptake of the toxin (A) into the host cell

Question 25

Superantigens, enterotoxins and neurotoxins are all examples of (endotoxins / exotoxins) released by bacteria…

Answer 25

Exotoxins

Question 26

Endotoxins are:

a) polysaccharides
b) lipoproteins
c) lipopolysaccharides
d) proteins

Answer 26

Endotoxins are:

a) polysaccharides
b) lipoproteins

c) lipopolysaccharides

d) proteins

Question 27

Endotoxins are responsible for which common symptoms of bacterial infection?

Answer 27

Fever, diarrhea, vomiting

Question 28

Inflammation is a ( specific / non-specific) reaction induced by _________ which leads to the accumulation of _________ .

Answer 28

Inflammation is a non-specific reaction induced by cytokines which leads to the accumulation of neutrophils.

Question 29

Diarrhoea is a typical symptom of gastroenteritis (inflammation of gastrointestinal system, usually caused by bacteria or viruses).

Differentiate between secratory and inflammatory diarrhoea 💩

Answer 29

• Secratory diarrhoea - no fever (e.g. V. cholerae)
• Inflammatory diarrhoea - fever, WBC in stool (e.g. Salmonella)

Question 30

Agents of infectious disease

What is the major virulence factor of E. Coli?

Answer 30

Fimbriae

Question 31

Agents of infectious disease

Vibrio choleraea (cholera)

Give a brief summary of transmission, virulence factors and treatment.

Answer 31

• Transmission: waterborne
• Virulence factors: Cholera toxin 1A + 5B encoded in phage genome (CTXφ) (see image for how the toxin works)
• Treatment: Electrolyte therapy

Question 32

Bacteremia

Answer 32

Presence of bacteria in the blood stream

Question 33

Septicemia

Answer 33

Septic shock - systemic inflammatory response to bacteria in the blood

Question 34

Agents of infectious disease

Salmonella enterica (Salmonella)

Give a brief summary of diseases caused and timeline of infection

Answer 34

• Diseases caused: Typhoid fever, gastroenteritis
• Timeline of infection:
  
  • 15 mins - invasion of epithelial cells
  • 1 hr - neutrophils increase vascular permeability
  • 3hrs - tissue dammage
  • 8hrs - massive effussion of neutrophils and fluid
  • 24hrs - evident tissue damage