Materials Included In Kit

Safety Precautions

This laboratory activity is considered nonhazardous. Follow all standard laboratory safety precautions.

Disposal

Materials may be saved and stored for future use.

Lab Hints

• Enough materials are provided in this kit for 30 students working in pairs or for 15 groups of students. All materials are reusable. This laboratory activity may reasonably be completed in one 50-minute class period. The Prelab Questions may be completed before coming to class, and the data compilation and Post-Lab Questions may be completed the day after the lab.
• Stress to students the importance of recording the number of each bacterial type in the data table before adding one more bingo chip of each type present as instructed in step 4 of the Procedure. If the population grows before the data is recorded students may be confused by the results.

Teacher Tips

• Discuss antibiotic-resistant strains of bacteria, such as Bacillus anthracis and methicillin-resistant Staphylococcus aureus (MRSA), that have posed major dangers to our society.

Answers to Prelab Questions

1. Why would a drug used to treat an infection 10 years ago not have the same effect today?

   As a result of over usage or misusage of antibiotic, bacteria have become resistant to the older generation of antibiotics.

2. Explain the effects of antibiotic resistance in society.

   The evolution or development of antibiotic-resistant bacteria results in the need for stronger antibiotics. It also results in increasing infection durations as well as the inevitability of antibiotics to treat infections. Antibiotic-resistant strains of bacteria lead to an increased death rate among the very young, the very old, and immuno compromised individuals. Antibiotic-resistant strains of bacteria are more costly to treat.

Sample Data

Answers to Questions

1. What general pattern was observed regarding the total number of bacteria present initially and the number remaining after eight doses?

   Answers will vary slightly. Overall the number of bacteria decreased from the initial count. Some groups may find the bacteria were completely eliminated.

2. Compare the initial and final counts of the least resistant bacteria. Explain any trend that was observed.

   Initially the least resistant bacteria were the most abundant bacteria found of the three bacteria present. However, the least resistant bacteria were the first to become eliminated by antibiotics as they are not as able to withstand the antibiotic effects as well as the other two bacteria.

3. Did all three types of bacteria—least-resistant, medium-resistant and highly-resistant—follow the same pattern during the eight antibiotic doses? Explain.

   No, they were different. The least resistant bacteria were eliminated first. The medium-resistant bacteria were eliminated but the count increased and decreased slightly before doing so. Some groups may find the medium-resistant bacteria to not be eliminated but they should decrease. In some cases, the highly-resistant bacteria may be eliminated but they may also survive in greater numbers than initially present depending if the antibiotic was always taken at the appropriate time.

4. Did any of the three types of bacteria have a greater population after antibiotic treatment than before? Why would this occur?

   The highly resistant bacteria population traditionally increases due to the fact that they are the most resistant to antibiotics and therefore may require stronger antibiotics or longer doses to be eliminated from the host.

References

“Antibiotics: Use them wisely.” Mayo Clinic. http://www.mayoclinic.com/health/antibiotics/FL00075 (Accessed May 2008)

Introduction

A scratchy throat, an earache or a cut that won’t heal—all could be signs of a bacterial infection. Antibiotics are prescribed to reduce the length and severity of infections. Antibiotics taken on time and finished completely are very effective. Study the effects of antibiotics on bacterial populations.

Concepts

• Antibiotic treatment
• Bacteria
• Antibiotic resistance

Background

Antibiotics are powerful drugs that are used to treat many serious and life-threatening diseases. Antibiotics are only effective against bacterial infections, some fungal infections, and some parasites. The principles of antibiotic treatment were actually discovered by accident in 1928 by Alexander Fleming (1881–1955). Fleming was culturing bacteria in glass dishes in his laboratory. However mold (fungus) had contaminated some of his bacterial cultures. He planned on throwing them away but instead noticed that no bacteria grew in the vicinity of the mold. The bread mold named Penicillium produces an antibacterial chemical named penicillin.

Since the discovery of penicillin, scientists have developed numerous antibiotics to help stop the spread of infectious disease. Although antibiotics have been proven very useful, misuse of antibiotics has become a serious problem. Frequent unnecessary use has resulted in the evolution of bacteria which are resistant to many common antibiotics. These extremely antibiotic-resistant bacteria develop because the original antibiotic failed to kill all of the targeted bacteria. As a result, the remaining bacteria survive and become resistant to the original antibiotic. Doctors then prescribe a different antibiotic, but resistant forms of the bacteria quickly develop the ability to withstand the new antibiotic as well, bringing about a continual cycle requiring different, more powerful drugs to treat infection.

As more bacteria become resistant to the original antibiotic, the consequences become more severe. Consequences include longer lasting illnesses, increased risk of serious complications and death. The inability of antibiotics to treat infection also leads to longer periods in which a person is contagious and able to spread resistant strains to other people.

Experiment Overview

This laboratory activity simulates what happens to a bacterial population when a person sick with a bacterial infection is treated with an antibiotic. Each color bingo chip represents a bacterium with a different level of antibiotic resistance. The red bingo chips are the least resistant bacteria, the blue bingo chips represent bacteria with medium resistance and the yellow bingo chips represent the most resistant bacteria. Based on the number rolled on the die, instructions are given which demonstrate the effects of taking or missing a dose of antibiotics.

Materials

Prelab Questions

1. Why would a drug used to treat a bacterial infection 10 years ago not have the same effect today?
2. Explain the effects of antibiotic resistance in society.

Safety Precautions

The materials used in this activity are considered nonhazardous. Please follow all laboratory safety guidelines.

Procedure

1. Obtain 20 red bingo chips, 15 blue bingo chips, 15 yellow bingo chips and one die. Place 13 red, 6 blue and 1 yellow bingo chip on the work surface in front of you and your partner. These chips represent harmful bacteria found in a patient’s body before beginning antibiotic treatment. Set aside the remaining bingo chips.
2. It is time to take the first dose of antibiotics. Roll the die and follow the key below.
   {10930_Procedure_Table_1}
3. Record the number of each remaining type of bacteria in the table on the Antibiotic Resistance Simulation Worksheet.
4. Bacteria are constantly reproducing in the host; in this case the host is the patient’s body. If one or more bacteria of a particular type (color) are still present in the patient’s body after the first dose (step 2), add one chip of that color to the population. Example: If the patient still has blue and red bacteria present, add one blue and one red chip to the population.
5. Repeat steps 2–4 at least eight times (or until all bacteria have been eliminated) to complete the table on the worksheet.
6. Using the data from the table, construct a graph displaying the number of each type of bacteria versus the number of doses. Use different color pencils to plot the following data: total number of bacteria, least resistant bacteria, medium resistant bacteria and most resistant bacteria. Connect each set of data points by drawing a colored line.

Student Worksheet PDF

10930_Student1.pdf