The Effectiveness of Garlic on Bacterial Growth

By Juliana Guarino

Purpose

• To test whether garlic and or garlic extract will have an effect on the growth of E. coli.

• Its been said that many herbs and spices, garlic specifically, can be used for antibacterial purposes.

Background Information

• Garlic was used medicinally dating back to the Neolithic Age

• It was used for protection against the Great Plague of London in 1665 and also during World War I

• Recent studies confirm that garlic is effective in inhibiting the growth of different bacteria, fungi and viruses

• The antibacterial properties are due to the allicin,C6H10OS2, that garlic contains. It stimulates the immune system by increasing the number of white blood cells called lymphocytes.

• If crushed or finely chopped, more allicin is produced• If cooked under high temperatures, the effectiveness of

the allicin will decrease.

Hypothesis

• All forms of garlic used will inhibit bacterial growth– The solution containing fresh, mashed garlic and sterile

water will be the most effective in doing so– The solution comprised of cooked, mashed garlic and

sterile water will be the least effective

1. 1.0g garlic powder and 10.0mL sterile water were combined and filtered into a small, sterile jar. This was specimen A.

2. One clove of fresh garlic was mashed to a pulp and combined with 10.0mL sterile water. It was then filtered into a small, sterile jar, creating specimen B.

3. Two sterile pipettes were used to extract 10.0 mL of organic garlic extract and 10.0mL of sterile water in a small, sterile jar. This was specimen C.

4. To create specimen D, 50.0mL of tap water was boiled in a beaker on a hot plate. Once boiling, one clove of garlic was put in the water for two minutes. The garlic was then removed and crushed with with 10.0mL sterile water and filtered into a small, sterile jar.

5. Specimen E consisted of the control, 10.0mL sterile water.

Procedure

6. The five jars containing the solutions were then autoclaved to prevent mold growth.

7. They were poured into five Petri dishes and labeled A-E. 8. Five blank discs were submerged into each Petri dish.9. The bacteria, E. coli, was hydrated and then evenly

streaked onto five different agar dishes using sterile technique.

10. Using sterile tweezers, one blank disc from each solution was added onto each of the five dishes.

11. The agar dishes were labeled 1-5 and taped shut. They were put in the incubator at 37oC.

Results and Data

A: Garlic Powder

B: Fresh Garlic C: Garlic Extract

D: Cooked Garlic

E: Sterile Water

Trial 1 0 0 0 11 0

Trial 2 12

Trial 3 12

Trial 4 13

Trial 5 13

Average 12.2

Zones of Inhibition (mm)

Results and Data

This graph shows the zones of inhibition produced from adding different forms of garlic to E.coliNotice that only solution D, cooked garlic, produced zones of inhibition.This suggests that cooked garlic is the only form of garlic that inhibits bacterial growth

A B C D E0

2

4

6

8

10

12

14The Effectiveness of Garlic in Fighting Bacteria

Different Solutions

Ave

rage

Zon

es o

f Inh

ibiti

on (m

m)

A- Garlic PowderB- Fresh GarlicC- garlic extractD- cooked garlicE- sterile water

Discussion

• Factors that could have affected results:– Garlic solutions were not concentrated enough– Autoclaving the solutions could have made the allicin

ineffective, similar to cooking. – The garlic not being used immediately could have

weakened the allicin – Not enough samples of fresh garlic

• Further Studies:– Use other forms of bacteria– Using an alternate heating method such as baking– Test in different temperatures

Discussion• First set of trials produced excessive mold growth, results

were inconclusive• To prevent this the solutions were autoclaved the second

time

Conclusion

• Cooked garlic was the only solution to produce zones of inhibition

• Hypothesis was rejected• Results are important to the world because it means

that cooked garlic can be used for certain antibacterial purposes.

References• Bacteria. (2010). In JRank Science Encyclopedia . Retrieved from

http://science.jrank.org/ pages/ 714/ Bacteria.html• Clark, M. (2005-2010). E. coli. Retrieved from

http://www.about-ecoli.com/• Dolby, V. (1999, July). Garlic: Strengthens our immunity,

improves infection-fighting ability. MoneyWatch, better nutrition. Retrieved from http://findarticles.com/ p/ articles/ mi_m0FKA/ is_n6_v58/ ai_18356463/

• Medham, T. (2003-2008). Garlic central. Retrieved from http://www.garlic-central.com/ antibiotic.html

• Sterile technique. (n.d.). Retrieved from http://www.umsl.edu/ ~microbes/ techniques.html

• Are there any questions?