Mac Agar Lab Report

In the first experiment to investigate how E. coli survives in food, bacterial growth significantly differed between my group’s nutrient agar and MAC agar plates. In courgette, there was moderate growth in nutrient agar while it was heavy in Mac agar. In beef broth, there was slight growth in nutrient agar while it was negative in MAC agar. In fresh basil, growth was heavy in nutrient agar while it was heavy in MAC agar. Where cottage cheese was the ingredient, both plates had heavy growth. For walnut, growth was slight in nutrient agar while it was negative in MAC agar.
Generally, the slight difference in bacterial concentration between the two plates could be because MAC agar inhibits growth of gram positive-bacteria and grows gram-positive bacteria while nutrient agar supports growth of fastidious microorganisms. The red color in the MAC agar plate indicates the presence of E. coli. Results from group A’s nutrient agar plate indicate that courgette, fresh basil, and cottage cheese appear to be contaminated with bacteria. Group A’s MAC agar plate indicates that courgette, and fresh basil may have had bacterial contamination with bacteria. Group B’s nutrient agar plate indicates that courgette, fresh basil, and cottage cheese appear to have bacterial contamination while courgette, fresh basil, and cottage cheese appear to be contaminated in
the MAC agar plate. Group C’s nutrient plate shows courgette and fresh basil may have had contamination while courgette, fresh basil, and cottage cheese appear contaminated in the MAC agar plate. Group D’s nutrient agar plate indicates fresh basil and cottage cheese may have been contaminated while the MAC agar plate indicates courgette and fresh basil may have been contaminated. Generally, results from nutrient agar and MAC plates indicate that courgette soup, fresh basil, and cottage cheese were mist likely contaminated with E. coli.
In the second part of the experiment, results indicate that bacterial growth was greatest where both agar plates were not refrigerated. Growth is also high where plates sat at room temperature for one and two days before being refrigerated. There is a slight difference in bacterial growth in the two agar plates. Bacterial growth is slightly lower in MAC agar plate, indicating that E. coli are likely to survive if the courgette soup is not refrigerated soon after it cools down. This indicates that my group’s courgette soup preparation is not safe. Results from different groups differed because of the difference in the soup preparation methods. In groups A and B, bacterial growth was slightly lower than group C and D. This is because heat treatment may have killed most bacteria. This indicates that courgette soup is safer if heat-treated and refrigerated immediately after cooling day.
Hand Washing
Hand washing, especially after visiting the toilet, is mandatory as it helps lower chances of infection from bacteria, especially E.
coli. In part one of the experiment to investigate the effect of hand-washing using different soaps, Hibiscrub had the best results with the least microbial growth after hand-washing. This is because the soap contains chlorhexidine gluconatem which is an antimicrobial agent (Netdoctor, 2014). Some students may have found microbial growth after hand-washing because of the paper towels they used to clean themselves with. In another way, microbial growth could be as a result of soap
contamination.
Results from part two of the experiment indicate that toilet paper does not provide an effective physical barrier against microorganisms. Groups 1—who neither used toilet paper or soap and Group 2—who used running water and paper towels had similar levels of microbial growth. On the other hand, Group 3—who washed their hands with soap and water and dried with paper towels, had the least level of microbial growth. For a food worker, these results indicates that the most appropriate procedure is two use two sheets of toilet paper in the toilet. After using the toilet, the worker should then clean her hands with soap and running water. Finally, she should dry her hands with paper towel. Generally, a food worker should wash hands thoroughly using running water and soap with antibacterial agents. The worker should then dry hands using paper towels before resuming duties (Food Standards Agency, n.d.). To make the results more reliable, I would increase the sample population and introduce more variables. For instance, introducing different kinds of soap, using stagnant water, and warm or hot water will give results that are more reliable.