Asceptic Techniques

Asceptic techniques method

• disinfect surfaces

• use sterile spreader to transfer bacteria

• remove bottle lid and flame neck of bottle

• keep lid over plate when working

• use sterile spreader

How to prevent contamination of bacterial culture

• keep the time spent with the lid off of the agar plate to a minimum

• Work near a Bunsen flame

• Use sterile equipment

• Regularly disinfect surfaces

Explain why the students passed the forceps through the bunsen flame before and after use

To sterilise bacteria and prevent contamination from unwanted bacteria

Inhibition zone

shows where the bacteria has not grown/has been killed

Penicillin and amoxicillin are the most common antibiotics used to treat strep throat.

Describe a laboratory experience that could be used to determine which antibiotic is more effective against the streptococcus bacteria.

• Use asceptic techniques

• Spread bacteria to agar plate

• Place paper discs soaked in each antibiotic on the plate

• Add control: paper disc soaked in distilled water

• Tape a lid on, invert and incubate and 25 degrees overnight

• Calculate the area of each inhibition zone using A= pi x diameter

• Then compare discs

Explain the appearance of agar plates after incubation

• inhibition zones show where the bacteria has not grown

• bacterium A killed by tetracyline (but tetracyline has no effect on bacterium B)

• bacterium B killed by penicillin (but penicillin has no effect on bacterium A)

• both bacteria resistant to streptomycin