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Two tests were carried out in the lab task. The first task was to detect E. Coli using anti-salmonella H antigen-antibody and anti-Shigella antibodies. This is a negative control because the control sample is the one that does not contain E. Coli. According to Tippe-Schindler et al. (2019), negative controls are used in a situation where absence is being tested. In such a test, the main idea is to look at cases where one can fail to detect the bacteria (Machnicka, 2020). The benefit of the negative control is that it enables one to know situations in which the bacteria can be detected and those in which it cannot be detected (Firstenberg-Eden & Sullivan, 2017). The expected result in this experiment is that increasing the proportion of salmonella in the sample will increase E.Coli contamination. This expectation is confirmed by the results where we have a titer cutoff of 1:1600. This means that with a salmonella concentration of 1600, an OD of 450nm will be greater than the cut-off OD. This shows that salmonella is a more effective predictor in the detection of E.Coli compared to shigella, which has a titer cut-off of 1:128000.
Sample 1(Anti-Salmonella H antigen-antibody) has a declining OD of 450 nm. It starts from a high and stabilizes as the titer increases (Zhang & Ji, 2017). This indicates that when the titer is low, there are large samples of OD 450 nm and vice versa. For Shigella antiserum, OD 450 nm was constant.
The other test carried out in this lab is determining the OD of E. Coli by ELISA assay 450nm. This is internal negative control. The difference between internal negative control and negative control is that the internal negative control is restricted to one sample (Johann, 2019). In this task, the control sample was created using Elisa assay. Still, for this one, results indicated a declining trend for OD 450 nm in E. Coli antiserum and a constant trend in Shigella antiserum.
The conclusion that can be made from this analysis is that the results are the same in both the internal negative control test and the internal control test. This further indicates that the two experimental techniques are sufficient for E. Coli detection. For the two samples, there was a more significant E. Coli presence in salmonella than in Shigella. Summarily, it is evident from the experiment that Salmonella bc E.coli is a negative control with a cross-reaction with the presence of an H antigen. The E. coli expressed negative control.
References
Firstenberg-Eden, R. and Sullivan, N. (2017). EZ Coli Rapid Detection System: A Rapid Method for the Detection of Escherichia coli O157 in Meat and Other Foods. Journal of Food Protection, 60(3), pp.219-225.
Johann, B., (2019). Detection of Pathogenic Escherichia coli (E. coli) Using Robust Silver and Gold Nanoparticles. Journal of Chemical Engineering & Process Technology, 04(08).
Machnicka, A. (2020). Escherichia Coli in Sewage Sludge – Detection Method / Escherichia Coli W Osadach Ściekowych – Metoda Wykrywania. Chemistry-Didactics-Ecology-Metrology, 19(1-2), 79-85
Tippe-Schindler, R., Zahn, G. and Messer, W., (2019). Control of the initiation of DNA replication in Escherichia coli. Molecular and General Genetics MGG, 168(2), pp.185-195.
Zhang, J. and Ji, H., (2017). An Anti E. Coli O157:H7 Antibody-Immobilized Microcantilever for the Detection of Escherichia Coli (E. coli). Analytical Sciences, 20(4), pp.585-58
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