Hence, if the bacteria has increased resistance, a smaller inhibition zone will be seen, and vice versa. The average class data for the diameters of the zones of inhibition were recorded in a lab notebook and the SIR table was used to determine whether each bacteria is susceptible (sensitive), unaffected (resistant) or somewhere in between (intermediate) for each of the antibiotics. The adult mentor of this experiment provided safety goggles, safety gloves, and a lab apron that were worn when handling the bacteria. All bacterial cultures were treated as potential hazards and tubes, pipettes, or other tools that come in contact with bacterial cultures were treated with care, in order to avoid ingesting or inhaling any bacteria. Ethanol also releases harmful vapors, so the experiment was performed in a well-ventilated room with windows open. Soap and water were used to cleanse after handling the bacteria. Bacterial cultures, plates, and disposables that were used to manipulate the bacteria were soaked in a 10% bleach solution (one part bleach to nine parts water) for one to two …show more content…
The petri dishes that contained erythromycin had the smallest inhibition zone measured, with an average of 33.7 mm. The primary purpose of the project was to accurately determine historical changes in antibiotic drug resistance. Based on the results of the experiment, it was concluded that tetracycline expressed the most resistance to E. Coli. This is because tetracycline is a broad spectrum antibiotic that acts against a wide range of disease-causing bacteria and because of its long use, it has less powerful abilities in hindering bacteria growth (McDermott, 2012). The hypothesis predicted that if if tetracycline was used, then it would be the least effective at impeding on the growth of the bacteria. They have been widely used for the past forty years as therapeutic agent in human and veterinary medicine but also as growth promoter in animal husbandry. The first tetracycline-resistant bacterium, Shigella dysenteriae, was isolated in 1953. Since then, tetracycline resistant pathogens have been on an upward trend and now occurs in an increasing number of bacteria (Chopra, 2001). Thus, its long history of usage translates to its increased amount of resistance to E. Coli. Its qualities as a broad spectrum antibiotic and its longer age relative to the other levels clearly outlines its declining capability as an antimicrobial.