How pathogens cause disease

Question 1

Koch’s postulates

Answer 1

The bacteria must be present in every case of the disease.
The bacteria must be isolated from the host with the disease and grown in pure culture.
The specific disease must be reproduced when a pure culture of the bacteria is inoculated into a healthy susceptible host.
Must be cultivated in the lab.

Question 2

Virulence postulates

Answer 2

Encoded DNA should be present and transcribed/translated in every case
Genes should not be present in a case that does not cause the disease
Introduction should transform a strain into one that does cause the disease

Question 3

UPEC, LEE and EHEC

Answer 3

UPEC - produces fimbriae
LEE - enteropathogenic E.coli
EHEC - 017: H7

Question 4

Endogenous infection

Answer 4

Bacteria in the wrong place i.e. endocarditis

Question 5

Exogenous infection

Answer 5

From other sources

Ingress or penetration

Question 6

S.aureus and M. tuberculosis

Answer 6

• S.aureus inhibits protein A
• M. tb prevents lysosomal maturation through:
  - SapM - inhibits phosphatidylinositide-3-phosphate
  - PtpA gene expression