core prac 15

Question 1

What are the independent variables for the antibiotics prac?

Answer 1

The type of antibiotic used.

Question 2

what are the dependent variables for the antibiotic prac?

Answer 2

The zone of inhibition left by antibiotic measured in cm2

Question 3

what are the control variables for the antibiotic prac?

Answer 3

• concentration of antibiotic used.
• type/amount of bacteria
• volume of antibiotic used for each disc.
• aseptic techniques should be used.
• pH of medium should be kept the same
• temperature should be kept the same.

Question 4

Should a control sample be used in the antibiotics prac?

Answer 4

Yes, some paper discs should be soaked with distilled water to make sure that it’s the antibiotic that’s killing the pathogen and not something else on the paper disc.

Question 5

Expected results for the antibiotic prac…

Answer 5

• Zone of inhibition is created as antibiotic kills the bacteria in the surrounding area and so leaves a clear ring that can be measured.
• Area of this ring is found and used to compare effectiveness of antibiotic.
• The more effective they are the larger zone of inhibition they will have.

Question 6

Method for the antibiotic prac…

Answer 6

1. Label 2 petri dishes for the antibiotic mast ring and the distilled water control.
2. use sterile forceps to place the mast ring onto their corresponding petri dishes, close each dish and seal with tape ensuring there’s a small grap to allow oxygen in and prevent the growth of anaerobic bacteria.
3. leave the cultures to incubate at 25 degrees for 24hours.
4. use a ruler to measure the radius of each zone of inhibition and then calculate the area using pie x r2