Core Practical 15

• What is the purpose of aseptic technique?

  To avoid contamination of the sample
• Why is aseptic technique important in experiments?

  It ensures reliable and repeatable data
• What can be measured to determine the effectiveness of antibiotics?

  Zone of inhibition
• What equipment is needed for the antibiotic effectiveness experiment?

  • Agar plate seeded with bacteria
  • Pipette
  • Bunsen burner
  • Disinfectant
  • Soap
  • Paper towels
  • Forceps
  • Antibiotic impregnated paper discs
  • Sellotape
  • Incubator
• What should be done to surfaces before and after the experiment?

  Wipe down with antibacterial cleaner
• How does a Bunsen burner help in aseptic technique?

  It creates convection currents to draw microbes away
• What should be done to the wire hoop before transferring bacteria?

  Flame the wire hoop
• Why should the neck of bottles be flamed before use?

  To prevent bacteria from entering the vessel
• What is the recommended action regarding the opening of vessels containing bacteria?

  Keep them open for the minimum time
• What should be done with windows and doors during the experiment?

  Close them to limit air currents
• What are the steps in the method for measuring antibiotic effectiveness?

  1. Use aseptic technique throughout.
  2. Flame forceps and pick up a paper disc.
  3. Lift lid of petri dish and place disc on agar.
  4. Tape the dish with two pieces of sellotape.
  5. Wash hands and disinfect the bench.
  6. Incubate for 24 hours at approximately 30 degrees.
  7. Measure the radius of the clear zone and calculate the area.
• What is a potential hazard when using disinfectant?

  It is flammable
• What safety precaution should be taken with a naked flame?

  Keep away from flammable materials
• What should be done in case of a fire hazard from a naked flame?

  Put out fire and seek assistance
• What is a biohazard risk in the experiment?

  Contamination
• What precautions should be taken to avoid biohazard risks?

  Use aseptic technique and wash hands
• What should be done if broken glass causes cuts?

  Elevate cuts and apply pressure
• How should data be presented after the experiment?

  • Plot a bar graph of type of antibiotics against area of clear zone.
• What does a larger area of the zone of inhibition indicate?

  More effective antibiotics against bacteria
• What factors affect the effectiveness of an antibiotic?

  Type of bacteria and antibiotic used
• What are the two types of bacteria mentioned?

  Gram-positive and gram-negative
• What is the relationship between antibiotics and bacteria in this experiment?

  • Antibiotics are tested for effectiveness.
  • Effectiveness is measured by the zone of inhibition.
  • Different antibiotics affect gram-positive and gram-negative bacteria differently.