Pathogens and host

Question 1

Name the 4 things that categorise infection

Answer 1

Inflammation
Pyrexia (fever)
Rigors
Tachycardia

Question 2

Pathogen

Answer 2

An organism which can cause disease

Question 3

Commensal

Answer 3

An organism which is part of normal flora eg Ecoli in gut

Question 4

Koch’s postulates

4 criteria for causative relationship between microorganism and disease

Answer 4

• Must be found in all cases of disease
• Culture ability outside body
• Reproduce on inoculation
• Microorganism should cause disease when introduced to a healthy individual

Question 5

Pathogenicity ( definition and the 2 categories)

Answer 5

Capacity of an organism to cause disease

Infectivity and virulence

Question 6

Infectivity

Answer 6

Ability to become established eg attachment and acid resistance

Question 7

Virulence

Answer 7

Ability to cause harmful effect once established which are conferred by 3 virulence factors

Question 8

3 virulence factors

Answer 8

Invasive, toxin production and evade immune system

Question 9

Invasiveness

Answer 9

Streptococcus pyogenes 
Necrotising fasciitis 
Cellulitis
Connective tissue breakdown eg collagenase
Fibrinolysis - streptokinase

Question 10

Endotoxins

Answer 10

Also known as lipopolysaccharide and are part of a gram negative bacterial cell wall

Question 11

Enterotoxins

Answer 11

Exotoxins which act on the GI tract eg vibrio cholera

Question 12

Exotoxins

Answer 12

Toxins released extracellularly by the microorganism eg clostridium tetani

Question 13

Superantigens

Answer 13

Certain exotoxins of staph aureus and strep pyogenes stimulate T cell division
When antigen specific is absent but overwhelming cytokine production ==> Toxic shock

Question 14

Innate immunity

Answer 14

Skin, gastric acid and mucous membranes

Question 15

Phagocytic cells

Answer 15

Macrophages - free in tissues or fixed in organs

Polymorphs which are short lived

Question 16

4 Polymorphs

Answer 16

Neutrophils - Bacteria
Eosinophils - allergen/ parasite
Basophils
Monocyte => Macrophage

Question 17

Are lymphocytes phagocytic?

Answer 17

No

Question 18

Opsonisation

Answer 18

Coated with antibody or complement and phagocytic cell detects both so efficient
Important for capsulate bacteria

Question 19

Monoclonal antibody

Answer 19

Specific for a single epitope

Question 20

Immunoglobulin

Answer 20

Proteins with antibody activity

IgM is primary, IgG is secondary and IgA for mucosal

Question 21

CD4

Answer 21

Helper cells Th1 - cell mediated immunity and activate macrophages - and Th2 - control B cell antibody response

Question 22

CD8

Answer 22

Suppressor and cytoxic cells which kill infected host cell or foreign cells

Question 23

Cell destruction following viral infection

Answer 23

Death of T4+ cells by HIV

Question 24

Virus induced changes to cellular gene expression

Answer 24

Cellular transformation by tumour viruses

Question 25

Immunopathogenic disease

Answer 25

Influenza A virus

Question 26

Overt disease

Answer 26

Visible

Question 27

Antigenic drift

Answer 27

Gradual evolution

Question 28

Antigenic shift

Answer 28

Significant antigenic structure change

Question 29

Acute infection

Answer 29

Influenza A or enterovirus

Question 30

Latent infection

Answer 30

Herpes simplex virus 2 types 1- cold sores 2 - genital lesions

Question 31

Tumour

Answer 31

HPV or retrovirus - lymphoma and leukaemia

Question 32

Asymptomatic

Answer 32

No symptoms - unapparent