Identifying an Unknown, Lab Report Example

Introduction

Understanding microbial flora is an essential component of understanding the human body and the health problems that we regularly face (Zimmer 1). When a patient is sick, it is necessary for the physician or health care professional to determine why. If the cause it bacterial, an essential requirement of this process is the determination of the microbe that caused the illness. These identifications must be precise, as the particular genus and species that is overgrown in a particular situation will have a direct impact upon the types of treatments that are prescribed.

The aim of this project is to identify the microbe isolated from a 14 year old female and a 16 year old female. An additional unknown was utilized. While this study will be observation driven, I hypothesize that Staphylococcus aureus will be discovered. This is a frequent bacterium that is found on people in general, and it is possible that the case in interest has been in recent physical contact with friends and family, allowing her to have more of this particular bacterium present that the average individual.

Methods

Unknown bacteria strains growing on blood agar plates and MacConkey plates were obtained. The blood agar plate was utilized to determine whether hemolysis occurs. The MacConkey plate was utilized to determine whether the bacteria is gram negative. These tests were followed by a coagulase test and a coagulant test to determine further information concerning the bacteria strains provided they appear to be positive. These results were provided for later analysis to compare with the API test results. To confirm results, a Novobiocin test was performed. Lastly, an API test was performed.

Results

An analysis of the isolant on the blood agar plate of the 14 year old female indicated that the bacterium was not hemolytic, gray in color, lactose fermented, and wet colonies. Furthermore, it was demonstrated that the bacteria is beta hemolytic and the strip test was negative. On the MacConkey plate, the colonies that grew were small, gram negative and appeared to be flat pink. The analysis of the isolant on the blood agar plate of the 16 year old female indicated that there were tiny gray colonies, which were gram positive. There was no growth on the MacConkey plate, although the gram positive nature of the test verifies that this bacteria is a member ofStaphylococcus. Since it was indicated that the test identified the bacteria is gram positive, a catalase and coagulant test were performed, indicating a positive catalase test and a negative coagulant test. Since both tests were not positive, the BioCHM test called the Novobiocin test was used. The Novobiocin result was over 16mm, indicating that the test was sensitive.

For the ONPG component of the API test, the yellow coloring indicated a positive result and the clear coloring indicated a negative result. For the amino acid tests, the cit was blue and therefore positive, the H₂S was black and therefore positive, the ure was hot pink and therefore positive, the toa was brown and therefore positive. The indole test was pink and therefore positive, as was the vp test. The gel test was black and therefore positive, and the carbohydrate test was yellow and therefore positive. Based on the information received in figure 1, there is an 87% likelihood that the unknown bacterium is Enterobacter asburiae and a 7.1% likelihood that the unknown bacterium is Serratialiquefaciens.

Discussion

If the experiment were to be repeated the experiment again, the results of the API test would be more accurate. The main problem that occurred during the experiment was that the test came out difficult to read because oil was potentially placed in the wrong spots. In addition, it is possible that the tubes were filled too high. Therefore, a drawback of this experiment was human error. Ultimately, the colors on the API test strip were difficult to determine because the chemical reactions that triggered a color change were incorrect because of the addition of the incorrect substrates. While human error is an unanticipated variable, future experiments will prevent these mistakes. Before beginning the procedure, it is important to ensure that experimenters have a higher level of training or practice.

An additional problem that was encountered during this experiment was that no growth occurred on the MacConkey plate for the second unknown. It is possible that not enough of the colony was selected when it was plated or that an error was made while spreading the colony. It is also possible that growth conditions were not sufficient for this type of bacteria. Therefore, it is possible that this bacterium in anaerobic and unable to live in an oxygen filled environment.

Overall, this experiment demonstrated that although it is difficult to correctly identify bacteria because there are many different features and characteristics to consider, this method is in fact possible. There are many tests, both technologically advanced and otherwise that can be used to determine characteristics of microbes including gram positive or negative status and membrane shape in addition to identifying a number of chemical properties. Understanding of these classifications allows scientists to eventually determine the exact genus and species that a bacteria is.

It is important to be able to identify unknown patient samples because unknown samples essentially reflect the types of samples that doctors and researchers need to identify in order to help their patients or to further their research. In large health care institutions, microbiology technicians are typically responsible for identifying the microbes that are causing patients to be sick, and they do so without ever meeting them (Ley 837). Therefore, hospitals have an unbiased way to define the sicknesses of their patients. A series of techniques similar to those used in these experiments are used for the identification process and this work helps many people who were hospitalized with serious bacterial infections to become healed.

Conclusion

In conclusion, it is possible to identify microbes using a variety of techniques. It is important to determine whether microbes are catalase positive or negative, gram positive or negatives, in addition to their sizes and shapes. This allows researchers to hypothesize what the unidentified bacteria is without completing further expensive tests. However, these additional technologies are necessary for the identity of the bacteria to be more certain.

The tests used for the second unknown indicated that the microbe in the 16 year old female patient had Staphylococcus, which was consistent with my hypothesis. While clear results were not received for the other tests, it is likely that the 14 year old female patient had a strain of Staphylococcusas well. More care will have to be taken in the future to ensure that the tests are done accurately so that more conclusive results could be presented. This experiment indicated that human error is common and it is necessary to repeat experiments many times before results can be confirmed.

Works Cited

Ley, R.E.; Peterson, D.A.; Gordon, J.I. Ecological and Evolutionary Forces Shaping Microbial Diversity in the Human Intestine. Cell. 124(2006): 837-848.

How to Write an Unknown Lab Report in Microbiology. PowerPoint.

Zimmer C. “How Microbes Defend and Define Us”. 12 July 2010. Web. 4 September 2014.