13 Communicable diseases

Question 1

what is vaccination?

Answer 1

deliberate exposure of an individual to antigens from a foreign source in order to provoke an immune response and provide immunity

(i.e. artificial active immunity)

Question 2

why does a vaccination work to prevent development of symptoms from infection?

Answer 2

generates a primary immune response and stimulates memory cells

∴ in future faster secondary response will occur following infection

Question 3

what is a live attenuated vaccine? what is a strength and

a limitation of it?

Answer 3

modified strains of bacteria/viruses that can multiply BUT are not pathogenic

+ strongest response and ∴ long-lasting immunity
- cannot be given to people with compromised immune systems

Question 4

what is a killed-inactivated vaccine? what is a strength and a limitation of it?

Answer 4

bacteria/virus is killed with chemical treatment, but antigens remain intact, provoking an immune response

+ more stable than live-attenuated, and does not require refrigeration
- provokes weaker immune response ∴ booster(s) needed

Question 5

what is a toxoid vaccine? what is a strength and a limitation of it?

Answer 5

toxoids are extracted and treated with formaldehyde to prevent symptoms –> triggers immune response and production of antitoxins

+ safe when toxins are reason for virulence
- does not give a strong immune response

Question 6

what is a subunit vaccine? what is a strength of it?

Answer 6

only specific antigens extracted and used

+ can construct vaccines for several strains

Question 7

what is an artificial antigen recombinant vector? what is a strength of it?

Answer 7

genes coding for the antigens of the pathogen are transferred through genetic engineering to harmless microorganisms

+ provides immunity to agents that can’t easily be attenuated without destroying antigen activity

Question 8

what is the aim of a vaccination programme?

Answer 8

to protect the population from a wide range of disease

Question 9

why are boosters used?

Answer 9

to increase the number of memory cells

increases speed of secondary immune response to destroy pathogen before it can cause disease

Question 10

how are vaccines used to prevent epidemics?

Answer 10

reducing chance of transmission

by increasing herd immunity

Question 11

what is ring vaccination?

Answer 11

a vaccination ring around the geographical centre of an epidemic to prevent its spread

Question 12

give three advantages of vaccination programmes

Answer 12

few/no side effects

economically viable for the whole population

easy to produce, transfer and store

Question 13

how can the mutation of a pathogen prevent a vaccine being effective?

Answer 13

change in genetic material causes change in antigens/glycoproteins

∴ previous vaccine no longer has complementary antibody ∴ cannot bind to antigen

Question 14

how can surface antigen variation prevent a vaccine being effective?

Answer 14

difficult to target all different antigens (especially if high mutation rate)

different strains in different geographical locations

Question 15

give three biological problems in implementing vaccines

Answer 15

live-attenuated pathogen could mutate and become virulent

storage/transport/distribution can be expensive if refrigeration is required

low nutritional state of target population may have weakened their immune systems

Question 16

what is protein energy malnutrition?

Answer 16

insufficient protein consumption

∴ can’t make antibodies/memory cells due to insufficient amino acids

Question 17

give an example of ethical issues surrounding vaccination testing

Answer 17

religious/cultural beliefs

lack of trust in government/health service

animal testing

side effects

ethics of pharmaceutical companies

consent vs. protection rights

Question 18

what vaccine is used against HPV?

Answer 18

subunit - contains proteins but no viral DNA ∴ no risk of infection

Question 19

what is an antibiotic?

Answer 19

a chemical that kills or slows down the growth of bacteria

Question 20

what type of cells do antibiotics have no effect on?

Answer 20

eukaryotic cells

viral particles

Question 21

what are bacteriocidal antibiotics? how do they work?

Answer 21

kill bacteria

by disrupting the cell wall or protein synthesis

Question 22

how does penicillin kill bacteria?

Answer 22

prevents synthesis of peptidoglycan cell wall ∴ no bacterium cell wall ∴ cell bursts

Question 23

how does polymyxin B kill bacteria?

Answer 23

damages plasma membrane by targeting phospholipids not found in eukaryotes –> contents of the cell leak

Question 24

what are bacteriostatic antibiotics? how do they work?

Answer 24

prevent growth/reproduction of bacteria

e.g. tetracycline prevents tRNA from binding to the ribosomes ∴ protein synthesis cannot take place

Question 25

what are sulphonamides? how do they work?

Answer 25

competitive inhibitors of bacteria membranes

inhibition of enzymes that assist in the synthesis of folic acid ∴ DNA (purines) can’t be synthesised

Question 26

how does erythromycin work?

Answer 26

blocks sites on ribosomes preventing protein synthesis

∴ polypeptide chain can’t be elongated

Question 27

what is the difference between broad and narrow spectrum antibiotics?

Answer 27

broad: work well against a wide range of bacteria
narrow: only effective against certain types of infection

Question 28

how does antibiotic resistance come about?

Answer 28

spontaneous mutation in the bacterium

∴ more tolerant to antibiotic

∴ more likely to survive

Question 29

how is antibiotic resistance prevented?

Answer 29

preventing misuse of antibiotics

completing the course

preventing damage to useful bacteria in the gut and microbiome

Question 30

outline some ways of reducing the spread of resistance

Answer 30

completing the course

reducing overuse

increased presence in animal feed

reducing contamination of door handles/equipment

aseptic techniques

isolating infectious patients

reducing use of anti-bacterial handwash