Bacterial Pathogenicity

Question 1

What parts of the body have low quantities of bacteria?

Answer 1

Fluids such as blood, CSF and urine
Tisssues and organs such as muscles, glands and brain

Question 2

Examples of bacterial virulence factors

Answer 2

Adhesins such as fimbriae, pili
Flagella (motility)
Factors to obtain nutrients eg sideophores for iron
Toxins
Capsule (prevents phagocytosis)
Type III secreted molecules (injected directly into host cell to allow bacterium to take over cells machinery)

Question 3

Meaning of overt/strict, opportunistic and facultative bacteria:

Answer 3

Overt = always cause disease
Opportunistic = when given the opportunity cause disease
Facultative = normally in environment

Question 4

What is an enterotoxin

Answer 4

Subgroup of exotoxins that affects the intestines specifically

Question 5

What is a toxoid

Answer 5

Inactivated toxin normally used in vaccines

Question 6

Definition of endotoxin

Answer 6

Exclusive to gram negative bacteria as possess LPS. LPS is cell bound and causes fever, diarrhoea and vomiting. Is weakly toxic

Recognised by TLR4 receptor

Question 7

Definition of exotoxin

Answer 7

Proteins releases extracellularly by both Gm+ and - species
Sensitive to heat and highly toxic

Question 8

Characteristics of streptococcus pneumoniae

Answer 8

Is a gram positive bacterium which has several virulence factors that enable it to cause damage to the host. For example it has
- capsule which prevents phagocytosis
- surface adhesins that attach to the respiratory lining
- secretory IgA protease that cleaves IgA
- neuroaminidase = cleaves neuraminic acids from sugar residues on host cell surface
-pneumolysins = pore forming that cause tissue damage

The response from the host is what causes pneumonia

Question 9

Clostridium botulinum is an example of a __________ . List the characteristic of this kind of bacterial infection

Answer 9

Is an exotoxin
Bacterium is gram a positive and anaerobic in nature and forms spores
Blocks ACh release in synapses leading to flaccid paralysis and respiratory arrest

Question 10

Cholera toxin is an example of a __________. Describe the characteristics of the illness caused by this bacterium

Answer 10

Gram negative bacterium (endotoxin) and also releases exotoxin (increased cAMP levels) that disrupts sodium/chloride balance which causes diarrhoea

Question 11

Salmonella characteristics

Answer 11

Gram negative rod shaped bacterium which is intracellular pathogen
Invades both phagocytic and non phagocytic cells and rearranges the cytoskeleton
Lives in the modified vacuole until cell lysis

Question 12

Strategies bacteria use for immune evasion

Answer 12

• hide in the cell and stay intracellular
• phase variation
• molecular mimicry
• modify or block host immune response through virulence factors
  Eg interference with host cells signalling pathways through secretion of type III molecules

Question 13

Pathogenicity islands definition and significance

Answer 13

Are regions on chromosomes that have been acquired through horizontal gene transfer. These regions give rise to specific virulence factors