Science Fair Project on
The Effect of Various Antibiotics on Bacterial Growth

Tips for Bacteria Science Fair Projects

Before you try out this project or a simliar one it is important that you learn more about bacteria and antibiotics. Background information on these two things will help you to create a hypothesis that will be functional. You can find information on these two subjects in your scienec textbook or online. Make sure your sources are valid and reliable before you rely on their information.

PURPOSE

The purpose of this experiment was to determine the effect of various antibiotics on the growth of bacteria.

I became interested in this idea when the doctor kept giving my brother antibiotics for ear infections. The antibiotics didn’t appear very effective. I wondered why. I am also interested in the medical field as a possible career.

The information gained from this experiment could benefit doctors when prescribing effective antibiotics for patients.

HYPOTHESIS

My hypothesis was that the antibiotic vancomycin would work the best. I based my hypothesis on statements by a hospital lab technician, Marie Clark. She said that in all her years of working at the hospital, vancomycin antibiotic worked the best.

EXPERIMENT DESIGN

The constants in this study were:
o temperature of incubation
o place bacteria grown (incubator)
o way bacteria and antibiotics are applied
o type and size of agar plate used to grow bacteria
o amount of antibiotics
o the time kept in the incubator
o number of hours bacteria has to grow
o grow bacteria on the same type of plate
o exposure to same bacteria
o kinds of pads used to apply antibiotic to plate
o amount of time the pads are soaked in the antibiotics

The manipulated variable was the type of antibiotic.

The responding variable was the amount of bacteria killed by the antibiotic.

To measure the responding variable the diameter of the death zone was determined in millimeters.

MATERIALS

PROCEDURES

1. Emulsify the bacteria type (collected from 18 to 24 hour non- selective agar plate) in sterile saline. Adjust the McFarland turbidity to .5 visually.
2. Soak the sterile Q-tip within 1 to 5 minutes of adjusting the turbidity. Turn the Q-tip many times, pressing firmly on the inside wall of the tube above the fluid level.
3. Swab the entire surface of the agar plate three times using the Q-tip, turning the plate 60 degrees between streaking to make sure to evenly coat the whole agar plate.
4. Leave the agar plate lid off for 3 to 5 minutes (but less than 15 minutes) for extra surface liquid to be absorbed.
5. Get out the chosen antibiotic discs and place on the surface of the agar plate. Add any extra discs with forceps.
6. Reposition any disc(s) that are not flat on the agar plate.
7. Turn plate upside-down (with lid on) and tap gently to be sure that all the discs stay on the agar surface.
8. 8. Place the upside-down agar plate in a 35 degrees Celsius, non-carbon dioxide incubator within 15 minutes of the disc application.
9. Incubate plates for 16 to 24 hours.
10. Examine the plate held a few inches above a black non-reflecting background with reflected light. Measure the diameter of the zones of death using the unaided eye. Calipers, ruler, or a template is held to the back of the inverted plate for measuring to the nearest millimeter.
11. Destroy all bacteria by using an autoclave on all contaminated items.

RESULTS

The original purpose of this experiment was to determine the effect of various antibiotics on bacterial growth.

The results of the experiment showed that the antibiotic vancomycin worked the best at killing the bacteria E. coli, Suitamonaus, Staphoreaus 1, Staphoreaus 2, and Streptococcus healacta.