Ewww! Kill it!

1. Ewww! Kill it! The effect of various household antibacterial cleaners on the zone of inhibition of bacteria Rebecca Rose EDCI 5724

2. Ewww! Kill it! • The problem: • Which antibacterial cleaner has the largest effect on the zone of inhibition of common household bacteria?

3. Ewww! Kill it! • What are zones of inhibition?: • Zones of inhibition are areas in which bacteria cannot grow around an antibacterial agent.

4. Ewww! Kill it! • The materials: • 10 sterile Petri dishes • digital camera • sterile tweezers • nutrient agar • raw hamburger (bacteria source) • clear metric ruler • 10 sterile swabs • black Pigma Micron pen • 50 sterile filter paper disks (6 mm in diameter) • 5 variables (antibacterial agents and one control) • Clorox bleach • Mr. Clean Antibacterial Multi-Purpose Cleaner • Scrubbing Bubbles Antibacterial Cleaner • Purell Hand Sanitizer with Aloe • Distilled Water (control)

5. Ewww! Kill it! • The hypothesis: • While the Clorox Bleach would initially have the largest zone of inhibition, the Mr. Clean Antibacterial Multi-Purpose Cleaner would have the largest zone of inhibition by the end of the experiment. • This was chosen because the Clorox Bleach was the only product that contained warnings about its ability to irritate skin, damage surfaces, and corrode metals at full strength and it was described as something that would break down quickly according to the website. • Next to the distilled water, the disc that would be surrounded by the smallest zone of inhibition would be the Purell Hand Sanitizer because of its evaporative nature and lack of long-term germ-killing abilities.

6. Ewww! Kill it! • The procedure: • Allow hamburger to sit at room temperature for one day. • Prepare the agar following the instructions provided with the bottle and set up 10 Petri dishes with equal amounts of agar. Allow agar one day to set. • Separate the discs into five groups of ten. Label all of the discs in each group with a number 1 through 5. • Assign each group to a specific agent and one group to be the control group. • Soak each of the groups 10 discs in the antibacterial agent that matches their number. Allow to air dry. • Soak the remaining group of 10 discs in distilled water. Remove excess liquid by lightly touching pooling liquid with the edge of a clean napkin. • Using the sterile swabs, collect bacteria by brushing swab gently over raw hamburger. • Using each swab only once, inoculate each Petri dish with the bacteria by rubbing the swab over the agar in a back-and-forth motion until the entire dish is covered. • Using tweezers, place one of each type of dot in each Petri dish equal distance apart from one another and 1.0 cm from the outer edge of the dish. • Cover dishes and allow to grow for 72 hours. • Using the digital camera, take pictures at 24 hour intervals to record growth and inhibition zones. To measure inhibition zones, lay the clear metric ruler over each dish and measure from the edge of each disc to the edge of the nearest bacteria colony.

7. Ewww! Kill it! • Setup – 0 Hours

8. Ewww! Kill it! • 24 Hours

9. Ewww! Kill it! • 48 Hours

10. Ewww! Kill it! • 72 Hours

11. Ewww! Kill it! • 72 Hours • Dish 1

12. Ewww! Kill it! • 72 Hours • Dish 2

13. Ewww! Kill it! • 72 Hours • Dish 3

14. Ewww! Kill it! • 72 Hours • Dish 4

15. Ewww! Kill it! • 72 Hours • Dish 5

16. Ewww! Kill it! • 72 Hours • Dish 6

17. Ewww! Kill it! • 72 Hours • Dish 7

18. Ewww! Kill it! • 72 Hours • Dish 8

19. Ewww! Kill it! • 72 Hours • Dish 9

20. Ewww! Kill it! • 72 Hours • Dish 10

21. The effect of various household antibacterial cleaners on the zone of inhibition of bacteria Averages Zone of Inhibition (mm) Chemical 0 24 48 72 1 90 31.9 28.4 24.8 2 90 12.6 8.4 5.9 3 90 9.2 6.2 5.1 4 90 6 3.3 3.1 5 90 15.3 9.4 6.3 Ewww! Kill it! • The results:

22. Ewww! Kill it! • The results:

23. Ewww! Kill it! • The conclusion: • That the bleach had the largest zone of inhibition was not incredibly surprising. • In my initial predictions, I forgot to factor in that I would not be diluting the bleach for the experiment. • As a result, there was little breakdown of the bleach and the bacteria therefore reacted most strongly to it.

24. Ewww! Kill it! • The conclusion: • However, the fact that the distilled water disc had the next largest zone of inhibition was surprising. Upon re-examination of the pictures taken during the experiment, it was concluded that the bleach disc provided some residual protection for the distilled water throughout most of the experiment. The zones of inhibition recorded for the distilled water discs are actually partially made up of the zones of inhibition resulting from the bleach discs.

25. Ewww! Kill it! • The references: • "Bathroom Cleaners by Scrubbing Bubbles". 2005. C. Johnson & Son, Inc. November 6 2005. <http://www.scrubbingbubbles.com/bathroom-cleaner/>. • BBS, NEWTON. "Ask a Scientist: Zone of Inhibition". 2004. (September 15, 2004). November 6 2005. <http://www.newton.dep.anl.gov/askasci/mole00/mole00531.htm>. • "Clorox Bleach Usage". 2005. The Clorox Company. November 6 2005. <http://www.clorox.com/solutions_reg_bleach.html>. • "Mr. Clean Tips and Uses". 2005. Procter & Gamble. November 6 2005. <http://www.mrclean.com/sites/en_US/mrclean/tips.shtml#cleaner>. • "Purell: Frequently Asked Questions". 2005. Pfizer Inc. November 6 2005. <http://www.purell.com/faq.aspx>.