Basics

Question 1

Reasons for return of bacterial infections

Answer 1

• Antibiotic resistance
• Emerging and re-emerging diseases
• Bioterrorism
• Outbreaks of water and food borne diseases
• Hospital acquired (nosocomial) diseases

Question 2

Definition of new-new diseases

Answer 2

Caused by previous unidentified microbes e.g Lyme disease

Question 3

Definition of new-old diseases

Answer 3

Diseases that have been known for a long time but now we know the cause e.g Campylobacter and Helicobacter pylori

Question 4

Definition of old-new diseases

Answer 4

Old disease with known causes once thought to be under control but have reappeared with new mutations e.g MRSA, Tb, E.coli, Influenza A

Question 5

Definition of old-old diseases

Answer 5

Old diseases with old causes but recently ‘discovered’ with respect to recognition of importance e.g Chlamydia.

Question 6

Definition of colonisation

Answer 6

Ability of a microbe to remain at a particular location and stay there.

Question 7

Definition of infection

Answer 7

Successful colonisation and multiplication by a microbe capable of causing disease.

Question 8

Definition of disease

Answer 8

A dynamic process involving a sufficient change in the normal function of an organism’s cells or tissues to cause symptoms.

Question 9

Definition of pathogenicity

Answer 9

A microbe’s ability to cause disease.

Question 10

Definition of virulence

Answer 10

The degree of pathology caused by a microbe.

Question 11

Definition of pathogenesis

Answer 11

Mechanisms a microbe uses to cause the disease state.

Question 12

Definition of virulence factors

Answer 12

Features that contribute to the ability of a microbe to colonise and cause disease.

Question 13

Definition of pathogen

Answer 13

A microbe capable of causing disease.

Question 14

Definition of True pathogens

Answer 14

Tend to produce disease readily in healthy hosts.

Question 15

Definition of opportunistic pathogens

Answer 15

Only cause disease in a compromised host or when a particular microbe enters an unusual site in a host.

Question 16

Name the 4 Koch’s postulates

Answer 16

1. The microbe must be associated with symptoms of the disease and be present at the site of infection.
2. The microbe must be isolated from disease lesions and grown as pure culture.
3. Culture microbe should reproduce the disease when inoculated into a susceptible healthy host.
4. The microbe must be re-isolated from the host in 3.

Question 17

What are the modern techniques used to satisfy Koch’s postulates.

Answer 17

1. PCR or immune-histochemistry can be used to detect the microbe.
2. Antibiotic therapy can be used to eliminate the disease.
3. Vaccination can be used to prevent disease.
4. Hygiene, disinfection and health practices can be used to prevent exposure to the microbe.

Question 18

What are the 6 molecular Koch’s postulates?

Answer 18

1. Identify gene responsible for virulence determinant.
2. The gene should only be found in strains of bacteria that cause disease and no in avirulent bacteria.
3. The gene should be isolated by cloning.
4. Distruption/knockout of the gene should reduce virulence.
5. Introduction of the cloned gene into an avirulent strain should confer virulence.
6. The gene should be expressed in the host during an infection.