Aseptic Techniques Flashcards
Risk assessment (3)
- Ensure that no members of the group are taking immuno-specific medication, as this may increase their risk of infection by the bacteria used.
• When using any commercial products, refer to manufacturers’ guidelines, avoid contact with eyes, and limit skin contact.
• Take particular care that ethanol used to sterilize instruments is kept away from lit Bunsen burners. Ethanol is HIGHLY FLAMMABLE
Benefits of using e.colo K12 strain
- is not thought to have any harmful effects, and is preferable because of its more rapid and consistent growth
Aseptic technique definition
Use of practices and procedures to prevent contamination of pathogens
Give five precautions used when growing microbes (5)
- not eating or drinking in the laboratory
- wiping down lab benches with disinfectant
- Not culturing microbes at body temperature
- using sterile inoculating loops for transferring cultures
- flaming necks of culture bottles to prevent contamination
How can agar dishes, culture media and other apparatus be sterilised ? (2)
- Using an autoclave
- A type of pressure cooker that uses high pressure steams at 120+ degrees to kill all living organisms
Method
- pass the metal loop through the flame of the Bunsen burner to sterilise it
- allow the metal loop to cool. If it is too hot it will kill any microorganisms it comes into contact with
- glide the loop over the surface of the agar without applying any pressure to ensure the metal loop has bacteria from the culture bottle over its surface
- sweep the neck of the bottle through the flame to destroy any airborne microbes. Replace lid of culture bottle to prevent contamination
What is the process of gliding the metal loop over the nutrient agar surface called ?
Plating
Why is it important to hold the Petri dish open at an angle rather than completely removing it?
This will reduce the chance of unwanted microbes from the air entering the dish and affecting results
What happens to the Petri dish?
- taped in four places
- incubated in an oven at 25 degrees. This allows microbes to grow and form colonies but is below body temperature, meaning pathogenic microbes that could harm humans will not grow
When carrying out the transfer, why is it important to work close to a Bunsen burner ?
So that the Bunsen flame can kill microorganisms in the air
How is the effect of different chemicals or antibiotic discs on growth of bacteria measured ?
Measure the diameter of any clear zones around the discs to compare antibacterial properties of the chemicals / effectiveness of antibiotics
How to make the results valid for the practical using antibiotic discs (4)
- Using The Same bacteria
- Same antibiotics
- Same Temperature
- no contamination (same conditions, Petri dish not left open)
- Aseptic techniques using in both
Controlled variable in the practical investigating effect of alcohol on growth of bacteria
- A disc dipped in sterile water should be used as a control.
What measurements can be made that will help you to compare the anti-microbial properties of the different substances
- A piece of squared paper under the agar plate might be helpful here.
- This is placed under the Petri-dish and the number of exposed whole squares are counted for each area and recorded in an appropriate table.
Conclusion
The greater the area affected around the paper disc, the more anti-microbial the substance.
