1. Preparation and Safety

1. Safety Precautions

   • Put on safety goggles and tie back long hair.

   • Disinfect the working area using an appropriate disinfectant, then wipe dry with paper towels.

2. Set Up Equipment

   • Place a Bunsen burner at your station and light it, leaving it on the safety flame.

3. Personal Hygiene

   • Wash hands thoroughly with anti-bacterial hand wash (avoid alcohol-based hand sanitizers to prevent fire hazards).

2. Preparing the Agar Plate

1. Label the Plate

   • Turn over the petri dish containing nutrient agar and label the underside with:

     • Your name/initials

     • The date

     • Your class

     • The name of the bacterial culture being used.

2. Divide the Plate

   • Draw three equal sections on the base of the plate and number them 1-3.

   • Place a dot in the centre of each section to indicate where the antiseptic discs will go.

3. Adding the Bacterial Culture

1. Flame the Bottle

   • Turn the Bunsen burner to a blue flame.

   • Unscrew the bacterial culture bottle lid, keeping the lid in your hand. Pass the bottle neck through the blue flame, twisting it as you go.

2. Collect the Bacteria

   • Use a 1ml syringe to collect 1ml of bacterial culture.

3. Flame Again

   • Pass the bottle neck through the flame once more, then replace the lid securely.

   • Place the bottle near the Bunsen burner.

4. Apply the Culture

   • Slightly lift the lid of the agar plate and dispense the 1ml of bacteria onto the agar surface.

   • Close the lid immediately.

   • Place the used syringe into a Virkon® disinfectant pot, ensuring it is filled with the liquid to fully disinfect it.

5. Spread the Bacteria

   • Use a sterile L-shaped spreader to evenly distribute the bacteria over the surface of the agar.

   • Discard the spreader into the Virkon® disinfectant pot after use.

4. Adding Antiseptic Discs

1. Prepare Antiseptic Discs

   • If making your own, soak three filter paper discs in different antiseptics.

   • Alternatively, use pre-impregnated discs.

2. Place the Discs

   • Slightly lift the petri dish lid again and, using sterile forceps, place one disc on the dot in each section.

   • Gently press each disc to ensure proper contact with the agar.

3. Record Placement

   • Make a note of which antiseptic/antibiotic corresponds to each numbered section for accurate results.

5. Securing and Incubating the Plate

1. Secure the Lid

   • Use two small pieces of tape to secure the lid, placing them on opposite sides of the dish.

   • This ensures the plate does not become anaerobic during incubation.

2. Incubation

   • Hand the plate to the Technician to incubate for 48 hours at 25°C.

6. Clean Up

1. Tidy the Area

   • Turn off the Bunsen burner and ensure it has cooled before handling.

   • Clean and disinfect the working area thoroughly.

2. Personal Hygiene

   • Wash hands thoroughly with hot water and anti-bacterial soap.

Video produced by @revisechemistrywithmrb practical GCSE Chemistry tutorials by a specialist Chemistry teacher with over 25 years experience teaching Chemistry and Biology.