Medical Microbiology Laboratory
Virginia Union University
Andrea R. Beyer
Spring 2013
Laboratory #7: Epidemiology Disease Detectives
Part A: Play the “Watersedge Public Health” GameThis portion of the lab is to be completed outside of the laboratory. To play the game, you will need a computer that has Adobe Flash Player installed on it (the game will tell you if you need to install Flash before starting, if the computer you are using currently does not have it.) Be sure to turn on the sound (speakers or use a headset) so that you can fully participate in the activity. The game can be found at:
Outbreak at Watersedge: http://www.mclph.umn.edu/watersedge/index.html, or you can Google “University of Minnesota Outbreak at Watersedge game”.
As you complete the game, fill out the questions in the lab report pertaining to the investigation. The game will take 15-25 minutes depending on how closely you follow directions, how fast you proceed through the various stages, and internet speed.
Part B: Outbreak in the Micro lab!
Today we will be simulating a disease outbreak in the laboratory. Each person will receive a tube of clear liquid which represents your bodily fluids. One person in each group will be “infected” with an illness, and it is your job as a group to determine which tube that is. You will move about the lab and mix your tube with other members of lab, to simulate interactions with other individuals in which disease transmission can occur (such as sneezing, coughing, kissing, transfer of blood, or sexual contact). Each person in the group will mix their tube with 3 different members of the group, and will then test their sample to see if they are “sick”. Each group member will report the order of their interactions with others on a group chart, and the outcome of their test (sick or not sick). As a group, you will then determine which tube number(s) started the “outbreak”; you should be able to narrow it down to two individuals, which you will then test to see who started the “outbreak”.
Good record-keeping is critical for the success of this lab; at each step of the simulation, record the number of the tube that you are mixing with in your lab report.
Note: The liquids in your tubes are harmless, and do not contain any microorganisms or real human bodily fluids.
Each student will need:
Sample tube of clear liquid (“body fluids”) with number/letter
Microtube
Micropipettor/dropper
Dip stick test
Procedure
1. Obtain a sample tube of clear liquid and record the number in your lab report. This is your tube of “body fluids” for today’s simulation. Write your name on your tube with a marker.
2. Transfer approximately 500 uL (0.5 mL) of your fluid into a microcentrifuge tube and label it with your name and tube number. This will serve as an original, unmixed sample in case you need to test it later. Set this tube in a rack with everyone else’s from your group.
3. When told by the instructor, you will find another person in your group to exchange fluids with. To do this, one of you will pour all of your liquid into the other person’s tube. Be very careful to not spill any of your liquid when you make the transfer! Mix the tube by gently inverting a few times with the cap on, and then pour half of the liquid back into the other person’s tube. After exchanging fluids, immediately record the tube number of your partner in your lab report.
4. When told by the instructor, you will find another person in your group to exchange fluids with (choose someone different than the person you just exchanged with). Repeat the fluid mixing as in step 3. After exchanging fluids, immediately record the tube number of your partner in your lab report for your 2nd contact.
5. When told by the instructor, you will find another person in your group to exchange fluids with (choose someone different than the two people you just exchanged with). Repeat the fluid mixing as in step 3. After exchanging fluids, immediately record the tube number of your partner in your lab report for your 3rd (final) contact.
6. Obtain a dip stick test- do not get the small square pad of the stick wet until you are ready to test your tube. While firmly holding the dip stick test by the white handle, briefly dip the blue-square pad into your tube of “body fluids”. Make sure that the pad is completely immersed in the liquid (about 1 second) and remove the test strip. Lay the test strip on a paper towel (test pad facing up) and wait 30 seconds. To read the test, you will be looking for a color change. Be sure to wait the full 30 seconds before recording the test result. If the sample is positive for the “disease”, it will turn brown, meaning that your tube is “sick”. If the sample remains a light blue color, it is negative, meaning that your tube is “not sick”. Record your findings in your lab report.
7. Next, you will enter your data on a group table. Write your name and your tube number in the first 2 columns, and then the tube numbers of your 3 contacts in the last 3 columns. Once everyone in your group has entered their information in the table, individuals in the group will “reveal” if they are sick or not by drawing a circle around their number in the third column of the group chart.
8. From here, you will work as a group to figure out who had the original “sick” tube. Think about each person’s interactions, and who ended up sick; in this simulation, who is sick is just as important as who is not sick in determining where the outbreak started. You should be able to narrow down the possibilities to 2 tube numbers.
9. To see if you are correct, go back to the tube rack containing the group’s original samples. Working as a group, use a dip stick test on the 2 tube samples that you think may have started the outbreak to see if the group is correct. Record your group predictions and the results in your lab report.
*Instructor’s Notes*
I used this activity for a laboratory of 29 students. I broke them into 2 groups; in order for the activity to “work” so that they obtain usable data, each group must contain at least 12 students. The initial “sick” tubes are simple glucose solutions, made by dissoloving an amount of laboratory glucose into water to get the desired concentration. The “test sticks” or “dipsticks” are a standard diabetic urine glucose test; for the test strips that I used, I cut off the extra, un-needed tests and gave the students only the stick containing the glucose test. The test sticks turn brown when dipped into a glucose solution (indicating a positive result). Using the product information sheet that came with the urine test strips, I determined a concentration of glucose that would give the most dramatic color change. I then multiplied that concentration by 8, because the original tubes need to be more concentrated as they will be diluted 1:2 over 3 mixings. The students should only mix with others in their group; if you have multiple groups, use different colored tubes and labels. For example, Group A has orange tubes and the samples are numbered 1-12, while Group B has blue tubes labeled A-L. For this exercise, I aliquotted about 5 mL of either water or glucose solution into 50 mL conical tubes, mostly to make it easier for the students to mix with one another without spilling. When it was time to mix, I announced that it was time to choose another partner and mix your samples. After the 3 mixing sessions, the students tested their “bodily fluids” to see if they were positive (brown strip) or negative (blue strip) for the “disease”. Then I had each group enter the letters/numbers of their mixing partners into a chart on a whiteboard, so that the entire group could see who-mixed-with-who and who ended up being sick. This is the same chart that they need to complete as part of their lab report (see below). Each group may have up to 8 people sick, if everyone chose someone else at random to mix with. The group then had to use logic and reasoning to figure out the potential index case… “whodunnit.” In most cases, they should be able to narrow it down to 2 individuals. To determine the identify of the index case, the students can use a test strip to test the original un-mixed samples of those 2 individuals (which they should have collected and set aside before the exercise). I had one case in which 4 students only mixed with each other, with one of them being the index case, so only those four became “ill” in that group It was impossible to know who might have started it, so the original sample of all four had to be tested to find the index case.
Lab #7 Epidemiology Lab Report: to be completed by the students and turned in during class the next week.
I discussed this lab a little more in my blog entry “My favorite lab so far… and half of it was not even in the lab.”
-Andrea R. Beyer, Ph.D.
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