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Biolabreport.1.100709

Biolabreport.1.100709 - Jacqueline Joseph Controlling the...

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Jacqueline Joseph Controlling the Growth of E. coli Using Antiseptics and Disinfectants Bacteria are found in almost every environment on Earth and they are necessary in maintaining optimum environments in animal and plant bodies in environmental systems (Pearson, 2009). Although bacteria can be beneficial, they also have the potential to cause disease. Bacterial pathogens form only a small part of the bacterial world, but they are able to enter the tissues of humans or animals and cause sickness and sometimes death (Smith, 2000). To cause disease the bacteria must damage the host (Smith, 2000). Therefore if the rate of growth is not controlled, bacteria can be completely destructive to its environment (Pearson, 2009). In the Escherichia coli bacteria, commonly known as E. coli, most strains are found to be harmless but some can cause serious food poisoning and serious illness. Controlling these harmful strains can be difficult but in most cases antiseptics and disinfectants are used to minimize growth. Common household disinfectants, such as bleach and Lysol, and common antiseptics, such as mouthwash, do not kill all bacteria, as would occur in sterilization, but they do reduce the number of bacteria on surfaces (Pearson, 2009), thus reducing the risk of exposure. In the present experiment, agar plates are used for bacterial culture. By utilizing two disinfectants and one antiseptic, it is possible to gauge how E. coli is affected and thus controlled. I hypothesize that both disinfectants and the antiseptic will be effective in reducing the number of E-coli on the agar surface. I predict that the disinfectants, bleach and Lysol, will be more effective than the antiseptic, mouthwash. A bacterial lawn was prepared by inserting a sterile swab into the E. coli bacterial culture. The entire surface of an agar plate was swabbed in two motions by angling the agar 45 ° and repeating after a 45 ° rotation of the plate. The agar surface was divided into four predetermined 1
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Jacqueline Joseph regions: control, disinfectant one (bleach), disinfectant two (Lysol), and antiseptic (mouthwash) (Figure 1). Disks soaked in sterile water and the respective disinfectants and antiseptic were placed on the agar in their specified regions (Figures 2). The agar plates were sealed with Parafilm and left to incubate at 37 ° C for 24-48 hours and then refrigerate for roughly a week. The next week, the zones of inhibition were calculated by measuring the area around the disk where bacteria growth had been inhibited (Pearson, 2009) and a gram stain of E-coli was performed.
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