Maths skills
Calculating the effect of antibiotics or antiseptics on bacterial growth
The effectiveness of the chosen antibiotic or A substance that kills or stops the growth of germs which cause disease. can be measured numerically by using the formula πr2, where r is the radius of the The area around an antibiotic or antiseptic on agar where bacterial growth is not visible. The size of the zone depends on how effective the antibiotic or antiseptic is..
Method
- For π use 3.14. This value may vary slightly in a specific question.
- Measure the diameter of the zone of inhibition and divide it by 2 to calculate the radius, (r), eg 10 / 2 = 5 mm
- Use the equation: πr2
For example: 3.14 × 52 = 3.14 × 25 = 78.5 mm2