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How to Write a Microbiology Unknown Lab Report

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Here is an excellent example of how to write an unknown lab report in Microbiology class. Please note that due to formatting issues the flow charts had to be removed. They would be in the Results section. All healthcare providers ultimately have to take a microbiology class as part of their program curriculum. So here is a great paper that might help you along when you are at this point in your studies.

UNKNOWN LAB REPORT

Unknown number 125

Clare Zilch

December 3, 2013

General Microbiology 203

 

INTRODUCTION

This study shows the importance of identifying unknown microorganisms by applying all the methods and techniques that were studied in the microbiology course throughout the semester.  By going through the steps to identify the microorganism, students began to comprehend infectious disease.  In the health field it is important for physicians to understand this so the patient can be accurately treated.  It is also important for students to understand sterile techniques, diagnostic steps, treatment, risk assessment, transmission, and prevention of microorganisms.  This study provides students with the knowledge they need for all of these.

 




MATERIALS AND METHODS:

The instructor handed out an unknown test tube, labeled as number 125.  The methods and tests learned through out the semester were used on this test tube in order to identify the two unknown microorganism; one a Gram positive and the other a Gram negative.  The laboratory manual, by McDonald, includes all the procedures used for these methods (1).

 

First the unknown tube was isolated. This was completed by taking an inoculating loop and spreading the unknown out on to a Nutrient Agar plate. This was done using the streak plate method, which is described in the lab manual. The bacterium were incubated and grown at 37 degrees for four days. Upon observation the isolation plate showed growth of two different colonies.  From there, each colony was isolated, incubated and grown on separate plates.  After the morphology was observed and recorded, a Gram stain was performed on each, this procedure is found in the laboratory manual.  The two microorganisms were identified; one was a Gram-positive bacteria, the other was a Gram-negative bacteria.  A series of biochemical tests were performed based on the results of the Gram stains.  The proper procedure for all of these tests can be found in the laboratory manual.

 

Table 1 lists the test, purpose, reagents and results for culture #1.

Table 2 lists the test, purpose, reagents and results for culture #2.

 

All of the following tests were performed on culture #1:

  1. Gram stain
  2. Simmons Citrate
  3. H2S
  4. Urea

 

All of the following tests were performed on culture #2:

  1. Gram stain
  2. Methyl Red
  3. Glycerol
  4. Maltose
  5. Oxidase

RESULTS:

In unknown tube #125 culture #1 appeared to be a white cloudy streak on the plate.  The Gram stain revealed it was Gram negative rods.  Culture #2 appeared to be solid white dots spread out on the plate.  The Gram stain showed it was Gram positive rods.  The results of the Gram stain determined which biochemical test to use in order to identify the microorganisms.  The tables below illustrate the tests used for each unknown microorganism.  The flow charts show how the conclusions were reached.

Culture #1 Biochemical Tests & Results

TEST

REAGENT OR MEDIA

TEMPERATURE

OBSERVATIONS

RESULTS

INTERPRETATIONS

Gram Stain Crystal violet, Iodine, Alcohol, Safranin N/A Red rods all over the slide; some in bunches, some alone Gram negative rods This bacteria is classified as a gram negative rod.
Simmons Citrate Citrate slant 37°C The tube stayed green Negative The bacterium is not able to utilize citrate as its sole carbon source.
H2S SIM tube 37°C No black appeared in the tube Negative The bacterium does not produce hydrogen sulfide
Urea Test tube of Urea 37°C The liquid in the tube stayed orange Negative The bacterium is not able to hydrolyze urea using enzyme urease

 

Culture #2 Biochemical Tests and Results

TEST

REAGENT OR MEDIA

TEMPERATURE

OBSERVATIONS

RESULTS

INTERPRETATIONS

Gram stain Crystal violet, Iodine, Alcohol, Safranin N/A Purple Rods all over the slide; some in bunches, some alone Gram positive Bacillus This bacterium is classified as a Bacillus
Methyl Red MRVP tube, Methyl Red reagent 37°C After adding the methyl red reagent the color did not change to red Negative The bacterium is not able to produce acid from glucose fermentation
Glycerol Fermentation tube 37°C The liquid in the tube did not change color Negative The bacterium does not ferment the carbohydrate glycerol
Maltose Fermentation tube 37°C The liquid in the tube stayed red Negative The bacterium does ferment the carbohydrate maltose

 

 

 




DISCUSSION/CONCLUSION:

The first culture’s results were found with the help of the unknown chart, handed out by the instructor.  The unknown tube, #125, was isolated in order to grow two separate cultures.  However, a problem was faced after the isolation was incubated.  The plate was contaminated and had more than two different bacterium’s growing.  A second isolation was completed and when observed there were only two bacteria’s growing.  After isolating one of the bacterium a Gram stain was performed.  The Gram test concluded that the bacterium was a Gram negative rod.  This narrowed down the unknown to 5 possible answers: Escherichia coli, Klebesiella pneumoniae, Enterobacter aerogenes, Proteus vulgaris, and Pseudomonas aeruginesa.  The first biochemical test performed was a Simmons Citrate, and after observation a negative result was concluded.  This narrowed down the answers to Escherichia coli and Proteus vulgaris.  The next biochemical test that was performed was a H2S test.  After observation, the H2S test had a negative result, which pointed to Escherichia coli.  A third test was done in order to confirm that Escherichia coli is the unknown.  The Urea test also had a negative result, which confirmed that the unknown #1 is Escherichia coli.

The second culture’s results were also found with the help of the unknown chart, handed out by the instructor.  The unknown tube, #125, was isolated in order to grow two separate cultures.  However, like stated earlier, a problem was faced after the isolation was incubated.  The plate had contamination, which prevented further testing from happening.  A second isolation was completed and when observed it confirmed that only two bacterium grew.  After isolating the second bacteria, a Gram stain was performed, hoping to see a purple color, indicating a gram positive.  Unfortunately, another issue arose.  When observed, there were both gram-positive rods and gram-negative rods.  This could have happened when attempting to isolate the bacterium on to two separate plates.  Because they were growing right next to each other, it was very possible to pick up both bacteria.  After being extra careful a second isolation was performed, and when the Gram stain was observed there were only Gram-positive rods.  This shows that there are 5 possible answers: Bacillus cereus, Bacillus subtilis, Staphylococcus aureus, Staphylococcus epidermidis, and Enterococcus faecalis.  However, because it was gram-positive Rods, this can eliminate the last 3, leaving Bacillus cereus and Bacillus subtilis.  A Methyl Red test was performed and had negative results.  This left Bacillus subtilis.  Glycerol and Maltose test were then performed in hopes of confirming this bacterium.  These tests were both negative, which confirmed that culture #2 was Bacillus subtilis. 

Escherichia coli, also known as E. coli, is a bacterium that is commonly found in the intestines of humans and animals.  It was first discovered in 1885 by pediatrician and bacteriologist, Theodor Escherich (2).  This type of E. coli exists as part of the normal flora that actually benefits the warm-blooded organisms (2).  One way this benefits humans and animals is by producing vitamin K2 (2).  However, not all E. coli is beneficial.  In fact, the strain 0157:H7, can be very threatening to humans, and in some cases can cause death.  Healthy adults will make a full recovery from this infection within a week.  However, young children, the elderly, and those with a weak immune system are at great risk if they catch this strain.  They could develop HUS (hemolytic uremic syndrome), a type of kidney failure, which can be potentially fatal (2).  The two easiest ways that humans can be infected are by ingesting contaminated water or ingesting contaminated food.  Some other ways include, having physical contact, contact with animals and high fiber diets (2).  Currently, there are no treatment options that can cure E. coli 0157:H7, but there are some easy measures that can be taken in order to prevent it.  The first step that should be taken very seriously is cook meat well, especially ground beef.  Second, people should know that pasteurized drinks are safer than unpasteurized.  Third, even though it might not protect you completely, wash vegetables as thoroughly as possible.  Fourth, make sure that all utensils and dishes used to cook are cleaned properly.  Finally, hand hygiene is the most important because it is the easiest way to spread disease.  Escherichia coli is a bacterium that we can’t live with, but that we can’t live without.  It is important for people to understand why it is beneficial for us, and even more important to understand how it is harmful.

REFERENCES:

  1. McDonald, Virginia, Mary Thoele, Bill Salsgiver, and Susie Gero. Lab Manual for General Microbiology. Meramec: St. Louis Community College, 2011. Print.
  2. “What Is E. Coli? (Escherichia Coli).” Medical News Today. MediLexicon International, 8 June 2011. Web. 23 Nov. 2013. <http://www.medicalnewstoday.com/articles/68511.php>.

 

 

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