Microbiology A2 - Mechanisms of Disease

Question 1

Basic Terminology

Define: Colonisation

Answer 1

The continuing presence of microorganisms without injury or invasion of our tissues.

Question 2

Basic Terminology

Define: Pathogen

Answer 2

An organisms that causes disease.

Question 3

Basic Terminology

Define: Infection

Answer 3

A microbe-induced state of disease.

Question 4

Basic Terminology

Define: Obligate pathogen

Answer 4

Microorganisms that must causes disease in order to spread, for example HIV

Question 5

Basic Terminology

Define: Conditional pathogen

Answer 5

Microorganisms that can invade tissues and cause disease when ideal conditions are met.
- For example, S. aureus infecting a surgical wound.

Question 6

Basic Terminology

Define: Opportunistic pathogen

Answer 6

• Microorganisms that would not normally causes disease but become pathogenic when the host defences are impaired.
• For example, Pneumocystis carinii in AIDS.

Question 7

How does influenza attach

Answer 7

Attaches via the haemagglutinin antigen

Question 8

How does Giardia lamblia attach

Answer 8

Attaches to gut mucosa using ventral sucking disks, causing local damage.

Question 9

How does P. falciparum attach?

Answer 9

Causes red cell protein expression enhancing adhesion of parasitized red cells to the epithelium of brain capillaries. Facilitates cerebral malaria.

Question 10

How does HIV attach?

Answer 10

HIV

• Binds strongly to the CD4 antigen, infecting T-lymphocytes that express it.

Question 11

Ability of microbes to survive and flourish once beyond natural barriers

Clinically relevant type examples: N. meningitidis

Answer 11

N. meningitidis

• Produces IgA protease, leading to barrier breakdown.

Question 12

Ability of microbes to survive and flourish once beyond natural barriers

Clinically relevant type examples: S. aureus

Answer 12

S. aureus

• Expresser of protein A, which inhibits complement activation.

Question 13

Ability of microbes to survive and flourish once beyond natural barriers

Clinically relevant type examples: S. pneumoniae

Answer 13

S. pneumoniae

• Has a specialized capsule that inhibits phagocytosis by neutrophils.

Question 14

Ability of microbes to survive and flourish once beyond natural barriers

Clinically relevant type examples: V. cholerae

Answer 14

V. cholerae

• A flagellated motile microbe, enhancing its virulence.

Question 15

What does Cholera toxin do?

Answer 15

• Cholera toxin: Stimulates diarrhoea via epithelial irritation of the gut.

Question 16

What does Tetanus toxin do

Answer 16

• Tetanus toxin: Disrupts neurological signalling and integrity.