Facilitator/Educator Guide: Stopping "Superbugs"
Antibiotic-resistant bacteria, also called "superbugs," are so common in the United States that more than 2 million people get infected with them each year. One way antibiotic-resistant bacteria can flourish is when a patient cuts short their prescribed course of antibiotics. Model how this can happen using a large set of dice.
Bacteria are microscopic, single-celled organisms that are found everywhere. They are in the environment all around us, as well as inside and outside of our bodies; they are ubiquitous. Most bacteria are harmless to humans, but some can cause serious illnesses. Antibiotics are the primary treatment for fighting bacterial infections. Before the discovery of the first antibiotic, penicillin, in 1928 by Alexander Fleming, people frequently died from minor wounds and infections (things we might think of as trivial injuries, like a scraped knee); today, penicillin is thought to have saved over 80 million lives.
However, many antibiotics have lost effectiveness because bacteria can become resistant to antibiotics over time, generating what are known as superbugs. In 2013, the Centers for Disease Control and Prevention (CDC) quantified the toll of superbugs, stating that they cause at least 2 million infections and 23,000 deaths each year. Carbapenem-resistant Enterobacteriaceae (CRE) and methicillin-resistant Staphylococcus aureus (MRSA) are examples of these superbugs.
Antibiotic-resistant bacteria can be created by inappropriately using, or misusing, antibiotics. There are many ways for antibiotic-resistant bacteria to come about, including when a person: takes antibiotics when they do not need to (e.g., the person has a viral infection, which cannot be treated with antibiotics), improperly disposes of antibiotics (e.g., pours them down a drain and contaminates water systems), or does not finish taking a prescribed course of antibiotics. The latter situation might happen because the patient forgets to take the antibiotics, feels better and stops taking them early, or dislikes the side effects of the antibiotics. All of these situations can result in selection for bacteria that are antibiotic-resistant because in a given bacterial infection, which can contain billions of bacteria, not all of the bacteria are the same, genetically. This difference in genetics make some bacteria more resistant to a certain antibiotic than others. If a patient stops taking antibiotics too early, it can help the tougher, antibiotic-resistant bacteria to grow.
In this science activity, students will use six-sided dice to model and explore how antibiotic-resistant bacteria can flourish when a patient cuts their prescribed course of antibiotics short while treating an infection. Note that this is only a general model of how antibiotic resistance may come about from this type of situation.
This science activity can serve as a starting point for a variety of science and health discussions. Here are a few examples of questions that can be used to start a discussion:
- Why should antibiotics not be used to fight infections caused by viruses?
- Can students think of times when they were prescribed antibiotics? What illness did they have?
- How can inappropriately taking antibiotics cause antibiotic-resistant bacteria?
- Can you think of examples of antibiotic-resistant bacteria? (Some common ones include Clostridium difficile, Neisseria gonorrhoeae, carbapenem-resistant strains of Enterobacteriaceae (CRE), and Methicillin-resistant Staphylococcus aureus [MRSA].)
- When were antibiotics discovered? How long have people been using them?
Needed for preparing ahead (quantities given for one student group; multiply as needed):
- Six-sided dice (100 total). They should be made up of three different colors in the following amounts:
- Six-sided dice, all of one color (70). Purple dice are used in the activity pictures. These can be purchased locally at a board game-related store or 100 same-colored dice can be purchased through an online supplier such as Amazon.com.
- Six-sided dice, all of a second color (25). Green dice are used in the activity pictures. These can be purchased locally or through an online supplier such as Amazon.com.
- Six-sided dice, all of a third color (5). Red dice are used in the activity pictures. These can be purchased locally or through an online supplier such as Amazon.com.
- Pot, box, or sealable plastic bag that is large and sturdy enough to hold all 100 dice (1). If you use a metal pot, you may also want to use a lid to cut down on the noise of rolling the dice.
Needed for each small group at the time of the science activity:
- A copy of the Student Guide for each small group (1)
- Six-sided dice, three groups of different colors as described above (100 total) in a pot or box
- Large, flat surface for pouring 100 dice onto (1)
- Pencil or pen (1)
Figure 1. You need only a few simple household materials and 100 dice to do this fun science activity.
What to Do
Prepare Ahead (< 10 minutes)
- For each small group, fill a pot, box, or sealable plastic bag with 100 dice total. The 100 dice should include 70 dice all of one color (purple dice are used in the activity pictures), 25 dice all of a second color (green dice are used in the activity pictures), and 5 dice all of a third color (red dice are used in the activity pictures). Set the pot aside until you are ready to do the activity.
Figure 2. For each small group, fill a pot or box with 70 dice of one color (purple is used here), 25 dice of a second color (green is used here), and 5 dice of a third color (red is used here).
Science Activity (20-30 minutes)
- Each small group should have 100 six-sided dice (of three different colors), a pot or box that is large enough to hold all 100 dice, a pencil or pen, and a copy of the Student Guide (it contains data tables that students will need to do the activity).
- Explain to students that they will be modeling how antibiotic-resistant bacteria can be caused by a patient cutting their prescribed course of antibiotics short when treating an infection. They will use 100 dice, which will represent the bacteria in a bacterial infection (where each die roughly represents 100 million bacteria). Some of the bacteria will be more resistant to the antibiotics than others, based on genetic differences. Rolling the dice will represent treating the infection with a dose of antibiotics.
- Ask students to identify what type of bacteria the different dice represent. The group of 70 dice (which are purple in the pictures and example tables) represent normal bacteria. The group of 25 bacteria (which are green) represent moderately resistant bacteria. The group of 5 bacteria (which are red) represent super-resistant bacteria.
Figure 3. Ask students to identify what type of bacteria the differently colored dice in the pot or box represent.
- Explain to students the mechanics of how the model will work. Each time a patient receives an antibiotic dose, the dice are rolled (dumped out of the pot or box). If any die shows a six when it is rolled, the bacteria it represents have survived a dose of antibiotics. If a die representing a normal bacteria shows any other number when rolled, the bacteria it represents have died from the antibiotics. If a die representing a moderately resistant bacteria shows a 4, 5, or 6 when rolled, the bacteria it represents have survived, but if their die shows a 1, 2, or 3 when rolled, the bacteria die. If a die representing a super-resistant bacteria shows any number except a 1, the bacteria it represents have survived. The table below is a summary of the different types of dice/bacteria and their outcomes:
|Dice description||Number of starting dice||Represents||Roll outcome|
|Bacteria survive if roll||Bacteria die if roll|
|Purple dice||70||Normal bacteria||6||1, 2, 3, 4, or 5|
|Green dice||25||Moderately resistant bacteria||4, 5, or 6||1, 2, or 3|
|Red dice||5||Super-resistant bacteria||2, 3, 4, 5, or 6||1|
- Let students know that they will fill out the "Full Course of Antibiotics" data table first. It will represent a patient taking antibiotics for a prescribed, full course. Students will then use this data to model treatments for patients with antibiotic courses that are shorter than what is prescribed.
|Full Course of Antibiotics|
|Number of Antibiotic Doses|
|Type of Bacteria||0||1||2||3||4||5||6||7||8||9||10||11||12|
- To fill out the data table, have students follow these steps:
- Fill in the number of normal, moderately resistant, and super-resistant bacteria in the "0" antibiotic doses column. (This should be 70, 25, and 5 dice, respectively.)
- Roll the 100 dice and carefully pour them out onto a large, flat surface.
Figure 4. Have students roll the dice onto a flat surface.
- Every die that is showing a 6 represents bacteria that survived the antibiotic dose. Remove these dice from the surface and place them back in the pot.
Figure 5. Have students put all dice that are showing a 6 back into the pot. These bacteria survived the antibiotic dose.
- Every moderately resistant (green) die that is showing a 4 or 5, and every super-resistant (red) die that is showing a 2, 3, 4, or 5, also represents bacteria that survived the antibiotic dose. Remove these dice from the surface and place them back in the pot.
Figure 6. Have students put all moderately resistant dice back into the pot that are showing a 4 or 5, and all super-resistant dice showing anything except a 1. These bacteria also survived the antibiotic dose.
- The remaining dice (normal [purple] dice showing 1–5, moderately resistant dice showing 1 or 2, and super-resistant dice showing 1) represent bacteria that did not survive the antibiotic dose. Set these aside; they will not be used in modeling the antibiotic treatment anymore.
- Separately count up the number of normal, moderately resistant, and super-resistant bacteria that survived the antibiotic dose (they should all be in the pot). Fill in the data table (in the "1" antibiotic doses column) with the results.
- Repeat this process 11 more times (or until no dice are left in the pot, if that happens sooner) so that 12 antibiotic doses have been modeled. Be sure students fill out the data table after each dose is modeled.
- Now have students use their data from modeling the full course of antibiotics to fill in the data table below, which will show how many, and which types, of bacteria would be left if that patient had shortened the length of their prescribed antibiotic course. Have students fill in the new data table using the related antibiotic dose columns from the first data table. In other words, the "Full Course of Antibiotics" column should be filled in with the data from their first data table after 12 doses were modeled, the "Antibiotics Course Cut Short" column with data from the column for 6 antibiotic doses, and the "Antibiotics Course Cut Very Short" column with data from the column for 3 antibiotic doses.
|Quantity of Each Type of Bacteria Remaining at the End of Each Patient's Course|
|Type of Bacteria||Antibiotics Course Cut Very Short: 3 Antibiotic Doses||Antibiotics Course Cut Short: 6 Antibiotic Doses||Full Course of Antibiotics: 12 Antibiotic Doses|
- You can ask students to look at the results from their data tables and discuss their results, such as how many super-resistant bacteria remained in each patient scenario, which type of bacteria was the most numerous by the end of each scenario, and how many antibiotic doses it took to kill all of the bacteria in the infection (if this happened).
You likely saw that in the model of a full course of antibiotics, all of the bacteria were gone by the end of the course, whereas bacteria still remained by the end of the shortened courses. Specifically, the course that was cut short probably had mostly super-resistant bacteria at the end, and the course that was cut very short probably had either moderately resistant or super-resistant bacteria as the most common types. (There is variation due to the randomness involved in the model.) While there are far fewer super-resistant bacteria in the initial infection, they are much harder to kill than the other bacteria types (in this model the odds of dying are 1 out of 6 for the super-resistant bacteria, compared to 1 out of 2 for the moderately resistant bacteria and 5 out of 6 for the normal bacteria).
For Further Exploration
This science activity can be expanded or modified in a number of ways. Here are a few options:
- Have students repeat this activity, but start with different numbers of normal, moderately, and super-resistant bacteria. How do their results change as the number of the different types of bacteria in the initial infection changes? How many antibiotic doses are needed to get rid of an infection that is mostly super-resistant bacteria?
- In this activity, students used probability, or the likelihood or chance that a certain event will happen, but they did not mathematically calculate the probabilities involved. You could have students calculate, for example, the probability of rolling a 1 on a six-sided die, or numbers 1–5 on a six-sided die. How do these probabilities relate to the model they tested?
- Have students pick a specific antibiotic-resistant bacteria, or other microbe, and do some research on it. With an adult's help, they can try to find out how common the bacteria is, why it is resistant to antibiotics, and what treatments are used. See if students can model the treatment of an infection with this bacteria.
- You could have students create a computer program to execute the model used in this activity. Doing this would allow them to easily and quickly explore many different permutations of the model.
CreditsTeisha Rowland, PhD, Science Buddies
Sponsored by a generous grant from Cubist