Infection and Response

• Antibiotics


  Medicines that help to cure bacterial disease by killing infective bacteria inside the body
• Clinical drug testing


  Drug testing done on healthy human volunteers and patients
• Communicable disease


  A disease that can be spread between individuals either directly or indirectly
• Double blind trial


  A study performed where neither the researcher or patient know whether the patient is taking the drug or a placebo
• Gonorrhoea


  A sexually transmitted disease (STD) caused by a bacterium with symptoms of a thick yellow or green discharge from the vagina or penis and pain on urinating
• Human Immunodeficiency Virus (HIV)


  An infectious virus that weakens the immune system and can lead to AIDS (acquired immunodeficiency syndrome)
• Malaria


  A disease caused by a protist that causes recurrent episodes of fever and can be fatal
• Measles


  A serious disease caused by a virus that shows symptoms of fever and a red skin rash
• Monoclonal antibodies


  Antibodies produced from a single clone of cells that are specific to one binding site on one protein antigen
• Non-communicable disease


  A disease which cannot be spread between individuals
• Non-specific defence


  General physical and chemical barriers that defend the body against lots of different types of pathogen
• Pathogens


  Microorganisms that cause infectious disease
• Placebo


  A substance designed to be indistinguishable from a drug being tested but has no actual effect on the patient
• Preclinical drug testing


  Drug testing done in a laboratory using cells, tissues and live animals
• Rose black spot


  A fungal disease where purple or black spots develop on leaves, which often turn yellow and drop early
• Salmonella


  A bacterial disease that is spread by bacteria ingested in food and can cause a fever, abdominal cramps, vomiting and diarrhoea
• Side effects


  Other additional effects that the drug has that are different from the expected effect of the drug
• Tobacco Mosaic Virus (TMV)


  A widespread plant pathogen affecting many species of plants which produces a mosaic pattern on the leaves and limits the plant growth
• Vaccination


  The process of introducing small quantities of dead or inactive forms of a pathogen into the body to stimulate the white blood cells to produce antibodies
• White blood cell


  An important type of cell that makes up the immune system and produces antibodies and antitoxins
• Pathogens


  Microorganisms that cause infectious disease
• Types of pathogens


  • Viruses
  • Bacteria
  • Protists
  • Fungi
• Viruses


  • Very small
  • Move into cells and use the biochemistry to make many copies of itself
  • This leads to the cell bursting and releasing all of the copies into the bloodstream
  • The damage and the destruction of the cells makes the individual feel ill
• Bacteria


  • Small
  • Multiply very quickly through dividing by a process called binary fission
  • They produce toxins that can damage cells
• Protists


  • Some are parasitic, meaning they use humans and animals as their hosts (live on and inside, causing damage)
• Fungi


  • Can either be single celled or have a body made of hyphae (thread-like structures)
  • They can produce spores which can be spread to other organisms
• Ways pathogens are spread

  • Direct contact
  • By water
  • By air
• Direct contact


  Touching contaminated surfaces, kissing, contact with bodily fluids, direct skin to skin, microorganisms from faeces, infected plant material left in field
• By water


  Drinking or coming into contact with dirty water
• By air


  Pathogens can be carried in the air and then breathed in (a common example is the droplet infection, which is when sneezing, coughing or talking expels pathogens in droplets which can be breathed in)
• Ways to reduce the damage of disease

  • Improving hygiene
  • Reducing contact with infected individuals
  • Removing vectors
  • Vaccination
• Improving hygiene


  Hand washing, using disinfectants, isolating raw meat, using tissues and handkerchiefs when sneezing
• Removing vectors


  Using pesticides or insecticides and removing their habitat
• Vaccination


  Injecting a small amount of a harmless pathogen into an individual's body, they can become immune to it so it will not infect them. This means they cannot pass it on.
• Herd immunity


  When a large proportion of the population is vaccinated, the spread of the pathogen is reduced as there are less people to catch the disease from
• Measles


  • Symptoms: Fever and red skin rash, can lead to other problems such as pneumonia (lung infection), encephalitis (brain infection) and blindness
  • How it is spread: Droplet infection
  • How it is being prevented: Vaccinations for young children to reduce transmission
• HIV


  • Symptoms: Initially flu-like symptoms, then the virus attacks the immune system and leads to AIDS (a state in which the body is susceptible to many different diseases)
  • How it is spread: By sexual contact or exchange of bodily fluids such as blood
  • How it is being prevented: Using condoms, not sharing needles, screening blood when it is used in transfusions, mothers with HIV bottle-feeding their children instead of breastfeeding, use of antiretroviral drugs (stop the virus replicating in the body)
• Tobacco mosaic virus


  • Symptoms: Discolouration of the leaves, the affected part of the leaf cannot photosynthesise resulting in the reduction of the yield
  • How it is spread: Contact between diseased plants and healthy plants, insects act as vectors
  • How it is being prevented: Good field hygiene and pest control, growing TMV-resistant strains
• Salmonella food poisoning


  • Symptoms: Fever, stomach cramps, vomiting, diarrhoea (all caused by the toxins they secrete)
  • How it is spread: These bacteria can be found in raw meat and eggs, unhygienic conditions
  • How it is being prevented: Poultry are vaccinated against Salmonella, keeping raw meat away from cooked food, avoid washing it, wash hands and surfaces when handling it, cook food thoroughly
• Gonorrhoea


  • Symptoms: Thick yellow or green discharge from the vagina or penis, pain when urinating
  • How it is spread: It is a sexually transmitted disease spread through unprotected sexual contact
  • How it is being prevented: By using contraception such as condoms and antibiotics (used to be treated with penicillin but many resistant strains are developing)