Effects of household cleaners on Escherichia coli Brian Agee Undergraduate Microbiology Major Department of Biology Tennessee Technological University Cookeville, TN Introduction -Thousands of people develop illnesses due to contact with Escherichia coli everyday. -Over the years, various disinfectants have been developed claiming to reduce the chances of coming into contact with this bacterium. (Levy 2001) -However, every year there are numerous cases in which someone becomes sick due to contact with Escherichia coli. (Rusin 1998) Objective The objective of my experiment is to determine if Escherichia coli is susceptible to common household cleaners, and in the process determine which cleaners are the most effective at inhibiting and killing the bacteria. Hypothesis Escherichia coli will be susceptible to the common household cleaners and therefore will not be able to grow in their presence. Results Assay 1:Disc Diffusion Assay Methods and Materials Two assays were used to determine the cleaning agents effectiveness against Escherichia coli. The procedure for both assays was performed according to that of Dr. Susan Goss. (Goss 2005) Assay 1: Disc Diffusion Assay - Determines the effectiveness of the cleaning agent at inhibiting Escherichia coli. - Each cleaning agent was applied to a disc and placed on a TSA plate with Escherichia coli. - TSA plates were then incubated for 48 hours at 35.6°C. - After the 48 hour incubation, the zone of inhibition was measured in millimeters. Assay 2: Tube Growth Assay - Determines the effectiveness of the cleaning agent as a bactericidal agent. - Escherichia coli was placed into a test tube with each of the cleaning agents and incubated for 48 hours at 35.6°C. - Samples from each test tube were streaked on TSA plates and also placed in the incubators for a period of 48 hours. - If growth occurred on the TSA plate, then the cleaning agent was ineffective at killing Escherichia coli. All cleaning agents that were tested were proven to inhibit Escherichia coli. Clorox bleach was found to be the best inhibitor, with a zone of inhibition 3-4 times greater than any of the other cleaning agents. Assay 2: Tube Growth Assay Conclusions As hypothesized, Escherichia coli was susceptible and did not survive in the presence of all of the cleaning agents. The most effective cleaning agent proved to be Clorox bleach, which had a zone of inhibition 3-4 times larger than any other cleaning agent tested. In order to keep our society healthy, cleaning agents must be used on a daily basis to prevent the spread of bacteria. Acknowledgements I would like to acknowledge Dr. Susan Goss, Professor of Biology at Tennessee Technological University for allowing me to use the Microbiology Laboratory and for all of the assistance that she provided. - All cleaning agents were effective at killing Escherichia coli, even when reduced by 50% concentration. - All cleaning agents were effective at killing Escherichia coli, even when reduced by 50% concentration. - The only growth occurred where the control, which consisted of nutrient broth and Escherichia coli, was streaked. - The only growth occurred where the control, which consisted of nutrient broth and Escherichia coli, was streaked. Cleaning AgentCloudiness (+/-) Growth (+/-) None++ Clorox-- Clorox (50%)-- Germ-X-- Germ-X (50%)-- Ajax-- Ajax (50%) (50%)-- Lysol-- Lysol (50%)-- Vinegar-- Vinegar (50%)--