4 - Bacterial Pathogenicity

Question 1

Define pathogenicity

Answer 1

ability of a microorganism to cause disease

Question 2

Define virulence

Answer 2

degree or intensity of pathogenicity

Question 3

Define pathogen

Answer 3

An organism that causes disease by impairing or interfering with a host’s normal physiological activities

Question 4

What’s the difference between infection and disease

Answer 4

In an infection, the bacteria will persist in a host without always causing damage where as a disease causes damage to the host and prevent the host from carrying out normal physiological functions

Question 5

What are opportunistic pathogens?

Answer 5

Pathogens that only cause serious disease when a host’s immune system is impaired

Question 6

What is a reservoir?

Answer 6

A place where microorganisms survive, multiply, and await transfer to a susceptible host

Question 7

What are primary pathogens?

Answer 7

Pathogens that can cause disease in healthy host I.e. those with out immune system defects

Question 8

Give some examples of bacterial reservoirs

Answer 8

Humans, animals and certain environments

Question 9

What are some examples of direct transmission of a pathogen?

Answer 9

Airborne (e.g via coughing and sneezing) and via body contact

Question 10

What are some examples of in direct transmission of a pathogen?

Answer 10

Via a vector (a living organism) or a vehicles ( non living materials or objects)

Question 11

What is colonisation?

Answer 11

The establishment of a stable population of bacteria within a host

Question 12

What are the two stages in adherence of bacteria

Answer 12

Association and adhesion

Question 13

What is the difference between association and adhesion?

Answer 13

Association involves non specific forces (such as charge) whereas adhesion involves specific bacterial adhesions and host receptors

Question 14

Give some examples of adhesins that bacteria can use?

Answer 14

Fibriae and pili, capsules and slime layers, flagella (only certain species) and lipoteichoic acids in gram positive bacteria

Question 15

Give some examples of host receptors used in bacterial adhesion

Answer 15

Blood group antigens and extra cellular proteins (such as collagen)

Question 16

What are siderophores are what do they do?

Answer 16

They are small molecules with a high affinity for iron that bind with iron and bring it into bacterial cells

Question 17

Give some examples of barriers to colonisation of pathogens in the body

Answer 17

Lyzozyme in eyes dissolves cell walls, the skin provides a physical barrier and produces antimicrobials, mucus in the lungs and flushing of the urinary tract prevents colonisation, stomach pH inhibits bacteria and our normal flora will compete with pathogens.

Question 18

What is invasion of bacteria?

Answer 18

When bacteria penetrate into, through or between cells

Question 19

How can bacteria resist phagocytosis?

Answer 19

They can produce structures that prevent contact with phagocytes such as capsules and specific surface proteins

Question 20

How can bacteria avoid antibodies?

Answer 20

They use capsules, the can change the antigens on their surface and sometimes they can degrade antibodies

Question 21

Give some examples of virulence factors

Answer 21

Toxins, extent of invasion

Question 22

Give some ways in which tissue damage can occur by bacteria

Answer 22

Direct and indirect effects of bacterial damage and an induction of autoimmune responses

Question 23

What is the difference between exotoxins and endotoxins

Answer 23

Exotoxins are proteins secreted from gram negative and positive bacteria and act on specific targets
Endotoxins are lipopolysaccharides on the membrane of gram negative bacteria that don’t have a specific target and can act on many host systems