Effectiveness of Essential Oils as Bacteria Inhibitors

In medieval times, waves of the Black Death epidemic were recorded throughout the world. Despite scant medical knowledge and poor recording of the disease events, it was found that quite a large number of people succumbed to the disease. Further in the 1600s and 1700s, there was an outbreak of the Bubonic Plague which continued haunting parts of Europe and the Mediterranean region. Nonetheless, confusion between the Black Plague deaths were differentiated with the Bubonic plague since it was found that bubonic plague Yersinia pestis . By this plague, people would die horrible deaths where they would be disfigured (Inglesby, et al., 2000). Because of this, people were so afraid to contract the disease that they would not touch the dead who succumbed to it. However, there arose legends of thieves who would rob the dead who died on the plague. Many versions of the stories existed, but all involved the use of the combination of herbal extracts which would ward off the plague. The exact herbs in their amounts vary from story to story. Some are effective in water while others are more alcohol-soluble. Others were soaked in vinegar to obtain purer versions of the same. The legends included the use of rosemary, orange, lemon, eucalyptus and clove.

Having established that the plague is caused by bacterium and the assertion that essential oils could have some inhibitory effect on the spread and growth of the bacterium, this experiment goes ahead to determine the inhibitory properties of such oils to prove or disprove legendary stories about the use of essential oils for this purpose. An essential oil is a highly hydrophobic substance that can be obtained from different plants. The liquid contains volatile aroma compounds that give the liquid unique properties under different conditions. It is essential in that it contains the essence of the plant (Reeds, 2000). Extracted by distillation or other chemical methods, they are used in the manufacture of perfumes, soaps, and flavor products among other things. The disk diffusion method is going to be used in this case to determine the inhibitory properties of the essential oil. This method employs the separation of sample bacteria which is allowed to grow overnight. It is then exposed to the test material to determine its growth after some time. The growth after the application of the tested material determines the inhibitory nature of the tested substance against bacteria (Boundless, 2013). This method will enable the experiment obtain valid results as to the inhibitory nature of essential oils to bacteria.

Central Question

This study revolves around the assertion that essential oils could be used as bacteria inhibitors in the times of the thieves to achieve effective stealing activities without contracting the bacterial bubonic plague. It is hypothesized that the use of essential oils among the thieves gave them inhibitory powers against the bacterial bubonic disease. This is because thieves who used some essential oil or a mixture of them could effectively steal from dead individuals who could still transmit the disease despite contact with the body. It is predicted that if essential oils do not have any inhibitory properties against the bacteria, it is likely that the thieves had some other method of protecting themselves such as immunity against the plague. Nonetheless, it is predicted that the thieves were successful if the inhibitory properties of the essential oils are found against bacteria.

Materials and Method

For preparation, all the necessary supplies were obtained. These include tubes of oils to be tested, sterile mineral oil, forceps, an alcohol jar, sterile filter paper disks, 1 mL pipette with its pipette pump, Mueller-Hinton agar plates and a glass L-rod. The petri dishes were properly labeled and divided into four sections. Each section was labeled with the oil being tested in it.

The spread plates were made thereafter. Here, the glass L-rod was placed in the alcohol jar alongside the forceps. Meanwhile, 0.1 mL of the bacteria species was pipetted onto each petri plate, placing the culture slightly off the center of the plate. The Bunsen burner was lit. The L-rod was removed from the fire and placed on the flame. Being removed immediately, the alcohol was allowed to burn off the rod and the rod was given some time to cool. The glass rod was used to evenly spread the bacterial culture around the Petri plate. For best results, the plate was span as opposed to spinning the L-rod. After each plate was spread, the L-rod was placed back in the alcohol and then re-flamed.

For the soaking and placing of disks, one first removed the autoclave tape from the filter paper disks sides as well as the paper towels. The forceps were removed from the alcohol jar and allowed to touch the flame. The forceps were allowed a few seconds to finish the alcohol burning and for the metal to cool down. After this, the forceps were used to carefully remove few pieces of the paper towel and place them on the desk. The forceps were now used to remove a single paper disk and dip it into the oil that was being tested. The disk was attached gently to the paper towel to remove excess essential oil on it. The proper sport on the petri plate was found, and the disk was placed at the center of the quadrant. The forceps were used to ensure that the paper stuck. The steps above were repeated for each essential oil. The forceps were cleaned in the alcohol jar and flame after handling each oil. Once all the disks were placed, they were left to incubate the petri plates at 37 °C. Below, one can see a pictorial of the experimental set up:

Table 1 : KB Test Summary Results

Results

It was noted that different oils had different capacities to inhibit on the growth of bacteria for the samples. It was noted, however, that essential oils had the least effect in Pseudomonas aeruginosa . This was with the exception of cinnamon oil, which achieved a total inhibition area of 15mm. Even thieves’ mix was incompetent against this bacteria sample. This bacteria is responsible for chronic pneumonia conditions. Escherichia coli, on the other hand, achieved high levels of inhibition in all essential oil samples, except mineral oil, where there was no inhibition at all. This bacteria is quite harmless to the individual, but could cause food poisoning in some cases (Vogt & Dippold, 2005). Staphylococcus epidermidis was equally responsive to all essential oils with the exception of mineral oil. This bacteria is especially common as a contamination on lab equipment and will normally grow on people undergoing catheters. It is responsible for reduced immunity for the victim (Queck & Otto, 2008). Bacillus cereus was equally responsive to almost all essential oils except the mineral oil. Notably, all bacterial species were responsive to thieves’ mix with the exception of Pseudomonas aeruginosa .

Results and Discussion

The experiment was out to prove the use of essential oils as inhibitors against bacterial infection, with specific regard to the use of the thieves’ mix to overcome the bacterial infection causing bubonic plague. Since the bubonic plague of this time was considered to be transmitted through contact with the infected person, it is possible that contact with a live victim would cause transmission (Ryan & Ray, 2004). However, thieves’ mix could adequately protect one against bacterial infection from the deceased person. This is because the pneumonic aspect of contraction was no longer present in the dead body. With regards to inhibition, one proves that mineral oil was simply not enough to protect oneself from the bacterial infection, since it does not offer sufficient inhibitory properties. This could explain why many people having normal oil on their skin could contract the disease. Nonetheless, any application of the essential oils on the person, including the thieves’ mix, could afford the person sufficient protection against the bacterial infection. Therefore, it is proven that through the use of essential oils, the thieves could access the belongings of the victims of the plague.

References

Boundless. (2013). Kirby-Bauer testing measures sensitivity of bacteria to antibiotics by culturing bacteria on solid growth media surrounding sources of drug. Retrieved from Boundless: https://www.boundless.com/microbiology/textbooks/boundless-microbiology-textbook/antimicrobial-drugs-13/measuring-drug-susceptibility-157/kirby-bauer-disk-susceptibility-test-791-6152/

Inglesby, T. V., Dennis, D. T., Henderson, D. A., Bartlett, J. G., Ascher, M. S., Eitzen, E., & Layton, M. (2000). Plague as a biological weapon: medical and public health management. Jama, 283(17) , 2281-2290.

Queck, S. Y., & Otto, M. (2008). Staphylococcus epidermidis and other coagulase-negative staphylococci. Staphylococcus: Molecular Genetics , 227-55.

Reeds, P. J. (2000). Dispensable and indispensable amino acids for humans. The Journal of Nutrition, 130(7) , 1835S-1840S.

Ryan, K., & Ray, C. (2004). Sherris Medical Microbiology (4th Edition). New York: McGraw-Hill Publishers.

Vogt, R. L., & Dippold, L. (2005). Escherichia coli O157: H7 outbreak associated with consumption of ground beef, June-July 2002. Public health reports, 120(2) , 174.