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NOVA scienceNOW: Killer Microbe

Viewing Ideas


Before Watching

  1. Assess student understanding of bacteria and antibiotic resistance. Write the following statements on the board or make a student handout without the answers. Have students vote on whether they think each statement is true or false. Keep a tally on the board of the responses to each statement. Then show the program segment. After students have viewed the segment, have them revisit the statements, correcting any wrong answers.

    • Bacteria are tiny, single-celled organisms. (true)
    • Bacteria are a form of microbe. (true)
    • There is only one type of bacteria. (false)
    • Bacteria are only found in our bodies. (false)
    • Bacteria can cause infections and illnesses. (true)
    • Bacteria are always harmful. (false)
    • A single bacterium can reproduce and give rise to five billion trillion bacteria in a single day. (true)
    • Bacteria can be passed from person to person by a handshake. (true)
    • Antibiotics are substances that control the growth of bacteria. (true)
    • Antibiotics can be used to treat infections, pneumonia, flu, and colds. (false)
    • There are many different types of antibiotics. (true)
    • If a bacterium becomes resistant to one type of antibiotic, it is resistant to all types. (false)
    • Antibiotic resistance can develop due to repeated exposure to antibiotics. (true)
    • Antibiotic resistance can be inherited. (true)
    • Antibiotic resistance can be passed from one bacterium to another through the exchange of bacterial DNA. (true)
  2. Demonstrate the rate of bacterial reproduction. Ask students which they would rather be given: (a) $10 a day for one month; or (b) one penny the first day of a month and double that amount on the next day, with subsequent doubling every day for the whole month. After students have answered, make a chart like the one shown below, and work as a class to determine the actual total amounts they would have at the end of each day.

     

    Daily Total

     

    $10 a day

    1¢ first day, doubled each following day

    Day 1

    $10

    Day 2

    $20 (10 x 2)

    2¢ (21)

    Day 3

    $30 (10 x 3)

    4¢ (22)

    Day 4

    $40 (10 x 4)

    8¢ (23)

    Days 5–29

    $10 more per day

    Exponential growth

    Day 30

    $300 (10 x 30)

    $5,368,709.12 (229)

    Explain that bacteria reproduce by doubling (using a process called binary fission which proceeds exponentially) termed exponential growth. Ask students how fast a single bacterium could develop into 5,368,709 new bacteria if each offspring divided every minute and none died. (It would take about half an hour.) Ask them what they think keeps bacteria from taking over the world at this rate of reproduction. (Accept all reasonable answers.)


After Watching

  1. Model the spread of bacteria in a human population. Demonstrate how easy it is for bacteria like A. baummanii to spread from person to person. Place a small amount of fine-sized glitter on the right palms of several students. If possible, use a different color of glitter for each student. Explain that the glitter represents bacteria. Have all the students circulate around the classroom, shaking hands with classmates. After a minute, have all students examine their palms and report the quantity and color of glitter. Discuss the results. What parts of the school building would have large deposits of glitter if everyone's hands were covered with it? (Doorknobs, desks, writing implements, lockers, computer keyboards, etc.) Brainstorm ways to avoid transmitting glitter. (Washing hands; using some sort of substance that prevents the glitter from sticking or that dissolves it; avoiding direct contact; using a barrier, such as gloves; and reducing the amount of glitter present in the environment.)

  2. Model the spread of antibiotic resistance in a bacterial population. Remind students that antibiotic resistance spreads when pieces of bacterial DNA (plasmids) are directly transferred between bacteria. The process is called conjugation.

    1. Before starting the activity, cut green and yellow construction paper into 1" squares. Make a total of 25 yellow squares. Then make 10 green squares per student.

    2. Prepare a small paper bag for each student. Five bags should each contain five yellow squares and five green squares. The remaining bags should each contain ten green squares.

    3. Draw the following table on an overhead or on the board.

     

    Number of students with yellow squares

    Number of students with NO yellow squares

    Before Exchange Round 1

    5

    class size minus 5

    After Exchange Round 1

     

     

    After Exchange Round 2

     

     

    After Exchange Round 3

     

     

    1. Hand out the paper bags. Tell students that the bags represent bacteria; the DNA of the bacteria is represented by the paper squares. Green squares represent bacterial DNA that is not antibiotic resistant, and yellow squares represent bacterial DNA that is antibiotic resistant.

    2. Have students walk around the room and exchange squares by taking a square from another student's bag without looking at it and then placing it in his or her own bag. They should do this until they have made ten exchanges.

    3. After the ten exchanges (the first round), have students count the yellow squares they have in their bags. Use the table to indicate the number of students with and without yellow squares.

    4. Have students continue exchanging for two more rounds of ten exchanges each. Tally the total number of students with and without yellow squares at the end of each round.

    5. Discuss the results with students. Ask:

      • How many bacteria were originally antibiotic resistant? (5)

      • How many bacteria were antibiotic resistant after the three exchange rounds? (The actual number will vary, but it should be greater than the original five.)

      • Suppose someone infected with these bacteria took an antibiotic. What would happen to the bacteria with only green squares? (The bacteria would all die.)

      • What would happen to the bacteria that had both green and yellow squares? (If the bacteria were resistant to that particular antibiotic, they would survive.)

      • What is the trend of antibiotic resistance seen in this simulation? (Antibiotic resistance increases with time and becomes an established characteristic in a population.)

  3. Develop a public relations campaign about antibiotic resistance. Explain that antibiotic resistance often emerges from the use and misuse of antibiotics. Discuss the problem of nosocomial infections and how hospitals are, ironically, the ideal environment for generating "super bugs." Divide the class into small groups, and explain that they will be acting as health professionals hired to develop a public relations campaign about antibiotic resistance. Then have each group create a two-part poster, which should include the information below. Display the finished products. Groups can present them to the rest of the class.

    Part 1: Describing antibiotic resistance

    • An explanation of antibiotic resistance and how it arises.

    • Information about how national and international agencies combat antibiotic resistance.

    • Tips for how the public can help combat antibiotic resistance.

    Part 2: Describing a known antibiotic-resistant infection

    • An example of a strain of disease- or infection- causing bacteria that are known to be antibiotic resistant, such as E. coli, Salmonella, Streptococcus pneumoniae, Mycobacterium tuberculosis, or Staphylococcus aureus, along with a list of any antibiotics to which the type of bacteria is resistant. If possible, describe the incidence of the bacterial strain throughout the U.S. or the world.

    • A description of preventive measures individuals can follow to avoid infection.

    • Steps individuals, communities, and health care facilities can follow to avoid the spread of infection.

  4. Show incidences of A. baumannii infection on a world map. Explain to students that a type of bacteria known as Acinetobacter baumannii has become one of the most worrisome sources of infections among troops wounded in Iraq. Since 2003, more than 700 U.S. soldiers have been infected. The first cases were reported in field hospitals in Baghdad. Since then, infections have been reported in hospitals in Afghanistan, Kuwait, Germany, and France, as well as in states in the United States that have military hospitals, such as Arkansas, California, Florida, Maryland, Tennessee, Texas, Ohio, and Virginia. Write these places on the board. Provide atlases and blank world maps (showing country divisions) to pairs of students and have them locate and label these areas. After they have completed their maps, ask students to consider how the infections might have spread from Iraq. As a class, discuss the role humans play in spreading bacteria. Reflect on the global ramifications of widespread travel, which is involved in activities such as war, vacations, and business. How might fighting a type of bacteria that has spread worldwide be different from coping with a local outbreak? (A local outbreak is easier to contain, study, and treat. A global outbreak strains medical resources and is hard to contain.) Write responses on the board.


Links and Books

Web Sites

NOVA scienceNOW
www.pbs.org/nova/sciencenow/0303/04.html
Offers resources related to bacteria and antibiotic resistance, including additional activities, streamed video, and reports by experts.

Alliance for the Prudent Use of Antibiotics
www.tufts.edu/med/apua/
The site offers information for consumers about efforts to promote the responsible use of antibiotics and how the public can help limit the development of antibiotic resistance.

Antibiotics Attack
http://www.hhmi.org/biointeractive/Antibiotics_Attack/frameset.html
Presents an interactive on what antibiotics are, their pathways of attack, and antibiotic resistance.

Antibiotics: The Untold Story (article)
www.prairiepublic.org/features/healthworks/antibiotics/index.htm
Examines our dependence on antibiotics as the most common treatment for illness.

Centers for Disease Control (CDC) Antibiotic/Antimicrobial Resistance
www.cdc.gov/drugresistance
Features information about when to use antibiotics, ways to prevent antibiotic resistance, diseases exhibiting antibiotic resistance, and steps federal agencies are taking to address the problem.

FDA Fact Sheet: Antibiotics
www.fda.gov/womens/getthefacts/antibiotics.html
Provides basic information about antibiotics and antibiotic resistance, as well as methods the general public can use to help control the spread of antibiotic resistance.

National Library of Medicine
www.nlm.nih.gov/medlineplus/antibiotics.html
The NLM's Antibiotics page contains detailed information and recent articles on antibiotics.

Stop Hospital Infections
www.consumersunion.org/campaigns/stophospitalinfections/learn.html
Includes numerous links to current articles relating to antibiotic infections in hospitals, as well as to types of antibiotic-resistant infections.

Wired Magazine: The Invisible Enemy
www.wired.com/wired/archive/15.02/enemy.html
Describes the impact and spread of A. baummanii.


Books

Antibiotics: Actions, Origins, Resistance
by Christopher Walsh.
Harvard University Press, 2003.
Describes how antibiotics combat infection and disease at the molecular level.

Good Germs, Bad Germs: Health and Survival in a Bacterial World
by Jessica Synder Sachs.
Hill and Wang, 2007.
Examines antibiotic resistance from both evolutionary and ecological approaches, and explores issues surrounding the hygiene hypothesis, an argument that links the over sanitation of modern life to now-epidemic increases in immune and other disorders.

The Killers Within: The Deadly Rise of Drug-Resistant Bacteria
by Michael Shnayerson and Mark J. Plotkin.
Back Bay Books, 2003.
A look at the overuse of antibiotics, the methods bacteria use to develop resistance, the role of antibiotics as animal-growth promoters, and the outlook for antibiotics.

The Other End of the Microscope: The Bacteria Tell Their Own Story
by Elmer Koneman.
American Society for Microbiology Press, 2002.
Tells the story of some bacteria upset at their continued mistreatment at the hands of humans.

Revenge of the Microbes: How Bacterial Resistance Is Undermining the Antibiotic Miracle
by Abigail A. Salyers and Dixie D. Whitt.
American Society for Microbiology Press, 2005.
Details the consequences of compromising one of our best weapons against disease—antibiotics.


Activity Author

Margy Kuntz has written and edited educational materials for more than 24 years. She has authored numerous educational supplements, basal text materials, and trade books on health, science, math, and computers.

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NOVA scienceNOW: Killer Microbe
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