rp6 - aseptic technique

describe the method for this aseptic technique practical:

1. carry out aseptic techniques detailed (e.g. flaming equipment, disinfecting surfaces)

2. use a wire hoop to transfer bacteria from broth to agar plate, flaming neck of bottle and wire hoop

3. spread bacteria evenly over plate using a sterile plastic spreader

4. flame and use sterile forceps to place a multi disc antibiotic ring on the plate, moving it by the centre

5. lightly tape a lid on, invert and incubate at 25°C for 48 hours

6. sterilise equipment used to handle bacteria and disinfect work surfaces

7. measure diameter of inhibition zone for each antibiotic and work out area using A = π d² / 4

8. (repeat to calculate a mean and SDs)

why do we not tape around the entire dish?

prevents O₂ entering, preventing aerobic respiration and so promoting growth of more harmful anaerobic bacteria

why do we place the dishes in the incubator upside down?

to reduce condensation dripping onto the agar surface

which type of graph should be drawn for this experiment?

bar chart (including SDs)

give the 7 main aseptic techniques that should be used in this experiment:

• wash hands w/ soap/disinfect surfaces

• use sterile pipette/syringe (i.e. flame)

• flame neck of bottle

• lift lid of agar plate at an angle

• work close to upward air movement

• use sterile spreader (i.e. flame)

• place pipette/spreader into disinfectant (immediately after use)

how does flaming and the use of a Bunsen burner maintain an aseptic environment?

creates a convection current so that microbes are drawn away from the culture (as air moves out from bottles - where relevant)

what concs can we draw from the results of this aseptic technique practical?

the larger the area of the inhibition zone, the more effective the antibiotic

describe the process of antibiotic resistance