Diseases and microbes

• vaccination – A small amount of dead or weakened pathogen containing an antigen that stimulates antibody production is injected into you.
• vaccination program – An organised approach to giving out vaccines so that most of the population are immunised e.g. all children given MMR at 6 months & 2.5 years.
• herd immunity – where if most of a population are immunised, then the un-immunised individuals are protected because they are less likely to have the pathogen transferred to them.
• epidemic – outbreak of a disease that spreads quickly within a region/country
• pandemic – an outbreak of disease that rapidly spreads across several regions/countries
• antigen – A substance on pathogens that stimulates the production of antibodies.
• antibody – A Y-shaped protein produced by the body that binds to antigens.
• immunisation – The process of protecting against infection by using a vaccine or Ab injection.
• immune response – The body’s defence against foreign material such as pathogens.
• immunity – The ability to fight infection by pathogens. It can be active or passive.
• lymphocyte – A white blood cell that produces antibodies.
• pathogen – A disease-causing micro-organism.
• phagocytosis – The process where a type of white blood cell called a macrophage ingests and destroys a pathogen.
• Vaccines contain a small amount of dead or inactivated pathogen particles.
• A vaccine stimulates white blood cells to produce antibodies and memory cells against the target pathogen, without making the person ill.
• If a vaccinated person is later infected by the same pathogen, the WBC’s of their immune system produce antibodies specific to the pathogen FASTER & IN LARGER AMOUNTS so it can destroy the pathogen very quickly, preventing infection.
• When pathogens enter the body, they multiply and make toxins. The pathogen or toxins may destroy the body’s cells and make the person feel unwell.
• Antibiotics are powerful medicines that help to cure many diseases by killing bacteria inside the body.
• Antibiotics cannot be used to kill viruses, as viruses replicate inside human cells. This means that it is difficult to develop drugs that kill viruses without also damaging the body’s tissues.
• Bacteria reproduce by binary fission.
• antitoxin - a protein made by a white blood cell capable of neutralising a specific biological toxin
• MMR protects against measles, mumps, and rubella.
• Strains of resistant bacteria are developing as a result of mutation and natural selection
• Measles is a virus. Viruses replicate inside human cells. It's difficult to develop drugs that kill viruses without damaging the body's tissues
• An example of an antibiotic-resistant strain of bacterium is MRSA
• How does a bacterial infection make someone ill?

  Bacteria reproduce quickly / increase rapidly in numbers and produce poisons/toxins
• How does a vaccine work?

  • Antibodies and antitoxins produced by white blood cells
  • Upon reinfection, antibodies are produced quickly
  • They destroy the pathogens
• We need to test drugs for efficacy, toxicity and dosage
• The heart drug digitalis originates from foxgloves
• Aspirin originates from willow
• Penicillin was discovered from penicillium mould
• Pre-clinical testing

  • Done in a lab
  • Focuses on efficacy, safety and dosage selection
  • Tested on cell and tissue samples then animals
• Clinical trials have three phases: phases 1, 2 and 3
• Phase 1

  • 20-100 healthy volunteers
  • Short trial
  • Low doses
  • Checks for safety and side effects
• Phase 2

  • 100-500 volunteer patients
  • Longer trial
  • Larger doses
  • Sees if the drug actually works and is effective
  • Establishes dosage
• Phase 3

  • 1000-5000 volunteer patients
  • Compares the drug with existing treatments or a placebo
  • Double blind trials
• Phase 4

  • Safety regulators decide whether the drug can be licensed
• Phase 5

  • After a drug is licensed, it can be prescribed by doctors