13 Communicable diseases Flashcards
what is vaccination?
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)
why does a vaccination work to prevent development of symptoms from infection?
generates a primary immune response and stimulates memory cells
∴ in future faster secondary response will occur following infection
what is a live attenuated vaccine? what is a strength and
a limitation of it?
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
what is a killed-inactivated vaccine? what is a strength and a limitation of it?
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
what is a toxoid vaccine? what is a strength and a limitation of it?
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
what is a subunit vaccine? what is a strength of it?
only specific antigens extracted and used
+ can construct vaccines for several strains
what is an artificial antigen recombinant vector? what is a strength of it?
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
what is the aim of a vaccination programme?
to protect the population from a wide range of disease
why are boosters used?
to increase the number of memory cells
increases speed of secondary immune response to destroy pathogen before it can cause disease
how are vaccines used to prevent epidemics?
reducing chance of transmission
by increasing herd immunity
what is ring vaccination?
a vaccination ring around the geographical centre of an epidemic to prevent its spread
give three advantages of vaccination programmes
few/no side effects
economically viable for the whole population
easy to produce, transfer and store
how can the mutation of a pathogen prevent a vaccine being effective?
change in genetic material causes change in antigens/glycoproteins
∴ previous vaccine no longer has complementary antibody ∴ cannot bind to antigen
how can surface antigen variation prevent a vaccine being effective?
difficult to target all different antigens (especially if high mutation rate)
different strains in different geographical locations
give three biological problems in implementing vaccines
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
what is protein energy malnutrition?
insufficient protein consumption
∴ can’t make antibodies/memory cells due to insufficient amino acids
give an example of ethical issues surrounding vaccination testing
religious/cultural beliefs
lack of trust in government/health service
animal testing
side effects
ethics of pharmaceutical companies
consent vs. protection rights
what vaccine is used against HPV?
subunit - contains proteins but no viral DNA ∴ no risk of infection
what is an antibiotic?
a chemical that kills or slows down the growth of bacteria
what type of cells do antibiotics have no effect on?
eukaryotic cells
viral particles
what are bacteriocidal antibiotics? how do they work?
kill bacteria
by disrupting the cell wall or protein synthesis
how does penicillin kill bacteria?
prevents synthesis of peptidoglycan cell wall ∴ no bacterium cell wall ∴ cell bursts
how does polymyxin B kill bacteria?
damages plasma membrane by targeting phospholipids not found in eukaryotes –> contents of the cell leak
what are bacteriostatic antibiotics? how do they work?
prevent growth/reproduction of bacteria
e.g. tetracycline prevents tRNA from binding to the ribosomes ∴ protein synthesis cannot take place
what are sulphonamides? how do they work?
competitive inhibitors of bacteria membranes
inhibition of enzymes that assist in the synthesis of folic acid ∴ DNA (purines) can’t be synthesised
how does erythromycin work?
blocks sites on ribosomes preventing protein synthesis
∴ polypeptide chain can’t be elongated
what is the difference between broad and narrow spectrum antibiotics?
broad: work well against a wide range of bacteria
narrow: only effective against certain types of infection
how does antibiotic resistance come about?
spontaneous mutation in the bacterium
∴ more tolerant to antibiotic
∴ more likely to survive
how is antibiotic resistance prevented?
preventing misuse of antibiotics
completing the course
preventing damage to useful bacteria in the gut and microbiome
outline some ways of reducing the spread of resistance
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
