The Anitmicrobial Effects of Garlic Extract on E. coli and Staphylococcus aureus

Naturally occurring plant products represent potential inhibitors of bacterial growth in the treatment of different diseases, and their medicinal benefits have been used for thousands of years. Garlic has been shown to be an... [ view full abstract ]

Naturally occurring plant products represent potential inhibitors of bacterial growth in the treatment of different diseases, and their medicinal benefits have been used for thousands of years. Garlic has been shown to be an antimicrobial agent to both Escherichia coli and Staphylococcus aureus. It is garlic’s unique chemical, allicin, that gives it its antimicrobial properties. It is also the same volatile molecule that gives garlic its unmistakable odor once it is crushed.

E. coli and S. aureus, while usually harmless, do have strains that can be very pathogenic to people. By studying the effects of garlic on E. coli and S. aureus at time-dependent measures, we can better determine whether the minimum inhibitory concentration (MIC) is bactericidal or bacteriostatic in each of the two bacteria. I hypothesize that when both Gram-negative E. coli and Gram-positive S. aureus are exposed to a certain low dose of garlic extract, the garlic is bacteriostatic. Because of the Gram-positive nature of S. aureus (having a thick peptidoglycan wall instead of a membrane rich in polysaccharides), garlic will show a stronger effect against S. aureus than when tested against E. coli. The critical window for bacterial growth observation is between 4-6 hours after the introduction of garlic in order to show restored bacterial cell growth. A fluorescent microscope can be used to determine bacterial cell viability after exposure to the garlic. Answers to this research will be helpful to both the medical world with treatment possibilities, as well as the food industries and food preservation techniques.