Effects of different antibiotics

Question 1

State the aseptic techniques.

Answer 1

-Close windows to limit air currents
-Wipe down surfaces with antibacterial cleaner before and after
-Use a Bunsen burner
-Flame the wire hoop before using it to transfer bacteria
-Flame the neck of any bottles before using them
-Keep all vessels containing bacteria open for the minimum amount of time

Question 2

Why is bacteria incubated at 25°C?

Answer 2

To prevent growth of pathogens, which occurs at higher temperatures.

Question 3

How can you compare the effectiveness of different antibiotics on the same bacteria?

Answer 3

Measure the diameter and calculate the area of the zone of inhibition on the agar.

Question 4

What does zone of inhibition indicate?

Answer 4

The bacteria killed by the antibiotic. The larger the zone, the more effective the antibiotic.

Question 5

State the hazards and precautions of this practical.

Answer 5

Naked flame: keep away from flammable materials, wear goggles, tie hair up
Bacteria is a biohazard
Disinfectant is flammable, keep away from naked flame

Question 6

Why should the lid not be completely taped to the Petri dish?

Answer 6

To avoid growth of anaerobic pathogens.

Question 7

Describe the graph that can be plotted from the results of this practical.

Answer 7

A bar chart of zone of inhibition against antibiotic.

Question 8

How is the control set up for this practical?

Answer 8

By placing a disc dipped in distilled water on the agar.