BIOS 242 Week 7 iLab: EPIDEMIOLOGY
EPIDEMIOLOGY
Introduction
I conducted a series of biochemical tests to identify the bacterium responsible for
... [Show More] the situation presented in the case study. This week’s case study illustrates a situation that an epidemiologist might need to solve. A rare expensive monitor lizard dies and the following day a Gila monster and rare Tibetan Newt died as well. A bacteriological survey of the reptiles and amphibians was obtained with the end result being salmonella bongori with gram negative rods.
Procedure
You will conduct four biochemical tests (Acid from Glucose, Gas from Glucose, Lysine decarboxylase, Malonate Utilization, Salicin fermentation, Sorbital fermentation, Growth in KCN, and Dulcitol fermentation) on your unknown bacterium sample. You may have noted that you have conducted several of these tests in previous weeks.
Conduct Acid from Glucose and Gas from Glucose Tests:
1. Click the New Unknown button and type Epidemiology in the “Enter a Label” field. Select Epidemiology 1 from the Subgroup dropdown menu.
2. Click the box allowing autoinoculation. Click OK. iLab: Epidemiology Page 3
3. Record your case study.
4. Record the results of the Gram Stain.
5. Open the Acid from Glucose Test from the Biochemical Tests Reference Book. Review the steps of this test and determination of test results. NOTE: You have conducted both of these tests in a previous week’s experiment.
6. Select Phenol Red Glucose Broth Durham Tube as your medium. Label the medium: PhenolRedGlucose. Click OK.
7. Inoculate your medium. Place in 37 degree incubator. Click Next Day.
8. Retrieve sample from incubator. Observe and record the results for Acid from Glucose and Gas from Glucose tests.
Conduct Lysine Decarboxylase Test:
1. Open the Lysine decarboxylase Test from the Biochemical Tests Reference Book. Review the steps of this test, including that you will record results after 24 and 48 hours. Make note of how you will determine the results of this test.
2. Select Lysine decarboxylase Broth as your medium. Label the medium: LysineD. Click OK.
3. Inoculate your medium. Place in 37 degree incubator. Click Next Day.
4. Retrieve sample from incubator. Note color of medium. Return your inoculated sample to the 37 degree incubator. Click Next Day.
5. Retrieve sample from incubator. Observe and record results. NOTE: To accurately interpret the results of this biochemical test, you must incubate for a total of 48 hours. A change from yellow back to purple at 48 hours indicates a positive result.
Conduct Malonate Utilization Test:
1. Open the Malonate Utilization Test from the Biochemical Tests Reference Book. Review the steps of this test. NOTE: You have conducted this test in a previous week’s experiment.
2. Select Malonate Broth as your medium. Label the medium: Malonate. Click OK.
3. Inoculate your medium. Place in 37 degree incubator. Click Next Day.
4. Retrieve sample from incubator. Observe and record the results. iLab: Epidemiology Page 4
Conduct Salacin Fermentation Test:
1. Open the Salacin Fermentation Test from the Biochemical Tests Reference Book. Review the steps of this test.
2. Select Phenol Red Salicin Broth as your medium. Label the medium: PhenolRedSalicin. Click OK.
3. Inoculate your medium. Place in 37 degree incubator. Click Next Day.
4. Retrieve sample from incubator. Observe and record the results.
Conduct Sorbitol Fermentation Test:
1. Open the Sorbitol Fermentation Test from the Biochemical Tests Reference Book. Review the steps of this test.
2. Select Phenol Red Sorbitol Broth as your medium. Label the medium: PhenolRedSorbitol. Click OK.
3. Inoculate your medium. Place in 37 degree incubator. Click Next Day. 4. Retrieve sample from incubator. Observe and record the results. Conduct Growth in KCN Test: 1. Open the Growth in KCN Test from the Biochemical Tests Reference Book. Review the steps of this test. 2. Select KCN (Potassium Cyanide)Broth as your medium. Label the medium: KCN. Click OK. 3. Inoculate your medium. Place in 37 degree incubator. Click Next Day.
4. Retrieve sample from incubator. Observe and record the results.
Conduct Dulcitol Fermentation Test:
1. Open the Dulcitol Fermentation Test from the Biochemical Tests Reference Book. Review the steps of this test.
2. Select Phenol Red Dulcitol Broth as your medium. Label the medium: PhenolRedDulcitol. Click OK.
3. Inoculate your medium. Place in 37 degree incubator. Click Next Day.
4. Retrieve sample from incubator. Observe and record the results.
View Lab Report Results:
1. Select “Lab Report” from the View item on the top menu bar.
2. You can copy and paste the contents of this lab report to a Word document and save. iLab: Epidemiology Page 5
3. Note that the lab report records the results of each of the five tests that you conducted on your sample. The lab report identifies the number of bacteria that were eliminated after each test. You will want to include this information in your lab report.
4. Also note that you do not know the identity of the bacterium that caused the infection.
5. After you have recorded the information on the lab report, close the document.
Determine Identity of Bacterium:
1. Open the Identification Matrix from the View Command. You will find that only possible bacteria that remain after conducting this series of tests will be shown on the Identification Matrix. Make note of the possible bacteria that might cause this infection.
2. From the Unknown command, select Identify. From the drop down menu, select a bacterium that is likely the cause of the agent (based upon the information you have from your tests and by viewing the Identification Matrix).
3. Click OK. Then, click Yes, when the Confirm Identification Window opens. A window will open letting you know if you chose the correct bacterium.
4. Now, open up the Lab report. Under the Identification Information of the lab report, you will see the bacterium that you selected and the bacterium that was assigned. You will also want to record this information in your final lab report.
Observations and Results
Result + or - Appearance after Incubation
Gram Stain Neg N/A
Acid from Glucose Pos Color Change
Gas from Glucose Pos Color Change
Lysine Decarboxylase Pos Color Change
Malonate Utilization Neg No Change
Salicin Fermentation Neg No Change
Sorbitol Fermentation Pos Color Change
Growth in KCN Pos Color Change
Dulcitol Fermentation Pos Color Change
Additional tests performed are listed below:
Result + or - Appearance after Incubation
Esculin Hydrolysis Neg No Change
DNase at 25C Neg NO Change
Hydrogen Sulfide Neg Color Change
Bacterium identified as: Salmonella Bongori with gram negative rods
Discussion
Identify the bacterium: Salmonella Bongori with gram negative rods
Is this infection local, systemic, subclinical, or focal? What evidence supports your selection?
• This type of infection is a subclinical infection because the animals in this case study carried it on the surface of their skin and it was transmitted to their foods and ingested by human hands, and transmitted from one animal to the other by means of manual transmission or potentially by means of raw foods.
Is this a primary infection, secondary infection, or nosocomial infection? Why?
• This infection is a nosocomial infection; it is the multiplication of microorganisms in the body. The hosts in this case could carry it on their skin and it can be transmitted from one animal to another through the food while they’re being fed.
What was the reservoir for this microbe?
• The reservoirs are body tissue, wastes, contaminated food and water as well as animals and insects.
Would this be classified as a communicable, a contagious, or a noncommunicable disease? Why?
• Yes, this would be a communicable disease because it is spread through the food and water.
In which disease category would this disease fall: acute, chronic, subacute, or latent? Why? –
• I would classify it as subacute because the symptoms of the disease were prolonged in the body but wasn’t chronic.
Conclusion
After conducting the lab experiment and observing the collected data, the conclusion was that the animals had salmonella from contaminated food that they had eaten from their handlers. This bacteria is subacute, meaning it is not chronic and can be avoided by washing hands thoroughly which helps prevent the spread amongst the food we handle. [Show Less]