Antimicrobial Effects of Cilantro

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Antimicrobial Activity of Cilantro on Staphylococcus Epidermis and Escherichia coli

Abstract
Antimicrobial effects of cilantro against the gram positive bacteria S. epidermis and the gram negative bacteria E. coli were looked at. We predicted that cilantro would act as an antibiotic against S. epidermis but not to E. coli because S. epidermis does not contain an outer membrane whereas E coli. does. We predicted that the semi-permeable outer membrane of E. coli would protect the bacteria from any antimicrobial properties of cilantro. A drop of cilantro juice and water in varying concentrations (1:10, 1:20, 1:40, 1:80) was added to a nutrient agar plate inoculated with S. epidermis and a nutrient agar plate inoculated with E. coli. The plates were incubated for 48 hours and then observed for a zone of clearing where the cilantro juice drop was placed. Cilantro was found to not display antimicrobial activity against either bacterium in the experiment in any of the different dilutions. These results could have to do with the possible contamination of cilantro or the specific bacteria we chose to target. Additional studies of cilantro should be conducted on different types of bacteria in order to gain a better understanding of how the herb works as an antimicrobial.

Introduction
Herbs and spices have been used for many years for their health benefits and antimicrobial properties (Lai & Roy, 2004). Cilantro, an herb found in many ethnic food dishes, has been shown to have an antibacterial effect on Salmonella choleraesuis due to the compound dodecanal found in the leaves. Dodecanal was found to be twice as potent as the antibiotic gentamicin that is commonly prescribed for Salmonella infections (Kubo, Fujita, Kubo, Nihei, & Ogura, 2004). The antimicrobial properties of cilantro have also been demonstrated against the bacteria’s Staphylococcus aureus, Bacillus cereus, Escherichia coli (Marsh & Arriola, 2009). We decided to conduct our own experiment to see if cilantro had any antimicrobial effect on the bacteria’s Staphylococcus epidermis and Escherichia coli. Experiments about the antimicrobial properties of herbs are interesting because their results can affect the way people choose to eat. For example, if a certain herb is found to delay food spoilage then perhaps people will choose to include it more often in their cuisines. Or, if a study finds that an herb has an antibacterial effect on an organism commonly found on produce, perhaps a fruit and vegetable wash could be produced that contains the herb in order to help prevent infection. We chose both a gram positive bacterium (S. epidermis) and a gram negative bacterium (E. coli) to see if a bacterial outer membrane would inhibit any antibacterial effect of cilantro. Gram negative bacteria have an outer membrane and gram positive bacteria do not (Tortura, Funke, & Case, 2010). We predicted that cilantro would have an antimicrobial effect on S. epidermis but not on E. coli. We inoculated two nutrient agar plates, covering each with one of the bacteria’s, and divided each plate into quarters. We then placed one drop of cilantro juice mixed with water in each of the four sections in different concentrations. This allowed us to see if a minimum concentration of cilantro was needed to produce an antimicrobial effect. We then incubated the plates at 37 degrees Celsius to allow the bacteria to grow and evaluated the plates after 48 hours. We expected to see a clearing of bacteria in at least one of the quadrants of the plate containing S. epidermis and did not expect to see any clearing of bacteria on the E. coli plate. Methods

1. Label one nutrient agar plate S. epidermis and one nutrient agar plate E. coli and divide each plate into quarters. Label each quarter with the different dilutions : 1:10, 1:20, 1:40, and 1:80. 2. Inoculate and label one water blank with S. epidermis and one water blank with E. coli. 3. Create a lawn plate of...
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