Aseptic techniques used to investigate the effect of antimicrobial substances on microbial growth

Question 1

Aseptic techniques used to investigate the effect of antimicrobial substances on microbial growth

Question 2

Describe what aseptic techniques must we use when carrying out this practical?

Answer 2

• wipe down surfaces with antibacterial cleaner, both before and after the experiment
• use a bunsen burner in the workspace so that convection currents draw microbes away from he culture
• flame the wire hoop before using it to transfer bacteria
• flame the neck of the bottle before to prevent bacteria in the air from entering the vessel
• keep all vessels containing bacteria open for a minimum amount of time

Question 3

How is the practical carried out?

Answer 3

1. Carry out aseptic techniques
2. Use a sterile inoculating loop to transfer bacteria to agar plate
3. Spread bacteria evenly by swirling petri dish or using a sterile plastic spreader
4. Flame neck of bottle
5. Add agar nutrients to the petri-dish
6. Using sterile forceps place 2 multi-disc antibiotic ring on a plate (penicillin and streptomysin). Ring should only be moved by holding the centre, not the arms
7. Lightly tape the lid, leaving enough for O2 to enter, invert and incubate at 25 degrees for 48 hours
8. Work out area of the inhibition zone using formula where Area = πr^2

Question 4

What are some Risks we need to make sure of?

Answer 4

• Bacteria - could lead to contamination - biohazard - aseptic techniques must be used
• Naked flame creating a convection current -tie hair up, keep away from flammable items
• Disinfectant - flammable keep away from naked flame