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Latex Vs. Silicone: A Study of Bacteria Present on Well-Baby Pacifiers Before and After Being Cleaned Using Two Common Cleaning Methods

Which Type of Pacifier is More Hygienic for your Child?

If you are a parent, have you ever wondered which pacifier will be better for your child? I know my parents have. When my sister was a baby, my parents wondered which pacifier was better, latex or silicone. Although they spent some time on the computer researching or talking to people about which they thought was a better, healthier choice, there was never really an answer. Because of this, I decided to take the initiative and find out which pacifier was healthier, after hand washing and boiling (with the least amount of bacteria), for my parents and other parents with this same question.

***If you're impatient and need to know the answer NOW, skip to the last page!!!***

Step 1: Purpose

The purpose of this experiment was to determine which type of pacifier, latex or silicone, harbors the least bacteria, before and after cleaning, and to determine the amounts of bacteria on the pacifiers.

Step 2: Hypothesis

It was hypothesized that silicone pacifiers will harbor less bacteria because they are more durable than latex. Because they are durable, they are more difficult to crack (cracking could lead to bacteria getting inside the pacifier) which means they should harbor less bacteria. After cleaning it in “a mother’s way” (handwashing with soap and warm tap water), and after boiling, it is hypothesized that silicone will still be cleanest because it began with less bacteria.

Step 3: Variables

-Independent (Manipulated) Variable - Pacifier materials and the cleaning methods (none vs. household cleaning vs. sterilization).

-Dependent (Responding) Variable - Bacterial growth.

-Controls - 6 unsucked pacifiers (1 of each material for each trial/condition).

Step 4: Materials

-Paper towels and Dial soap (for hand washing)

-1 box of latex medical exam gloves

-1 pair of laboratory goggles

-18 swabs in sterile packages

-18 prepared petri dishes with lids (with agar)

-1 black permanent marker (for marking petri dishes and cups holding pacifiers)

-1 lab coat

-18 pacifiers used by well-children (9 latex and 9 silicone)

-24 new pacifiers - BPA free (including extra in case more must be collected to obtain equal numbers of silicone and latex)

-1 incubator

-1 digital camera

-Clear tape used to seal petri dishes

-24 Sterile urine collection cups/bags (to collect pacifiers)

-24 survey forms to give to participants saying: What type of pacifier (latex or silicone)? If you do not know, what is the brand? How long has your child been using this pacifier? How often do you clean it and how do you clean it? How old is your child?

-9 large Ziploc storage bags

-1 pot (to boil pacifiers in)

-1 Celsius thermometer

-1 stove / burner

-Distilled water

-Metal Tongs

Step 5: Procedure (I Tried to Be As Thorough As Possible. Be Prepared - It's VERY Long)

PART 1

1)-Develop research plan and visit malls to determine locations of children’s playgrounds.

2)-Consult with qualified scientist and lab director at a certified lab regarding proper sample collection, procedures, and safety.

3)-Conduct research regarding the brands and types of pacifiers that are available for purchase. Create a spreadsheet with information about the pacifier brands, identifying features, and whether they are latex or silicone.

4)-If needed, submit research plan for approval to qualified scientist and lab director.

5)-Plan 2 days to collect pacifiers at 2 different children’s mall playgrounds.

6)-Purchase approximately 24 brand new pacifiers (12 silicone and 12 latex).

7)-On day one, go to a mall with qualified microbiologist.

8)-Collect 18 pacifiers (9 latex and 9 silicone). Continue to collect pacifiers until appropriate numbers are obtained.

9)-Bring sterile bags/sterile urine collection cups, gloves, a black permanent marker, and 24 new pacifiers.

10)-Locate children’s mall park.

11)-Put on gloves.

12)-Locate parent/guardian with a child using a pacifier.

13)-To eliminate risk if you are a student researcher, have a designated supervisor approach parents and politely ask them if they would like to participate in this project to try to determine whether latex or silicone pacifiers harbor the least bacteria.

  • a)-Make sure that the child is currently asymptomatic and could be classified as a “well-baby.”
  • b)-Also make sure that the child is 2 years of age or younger. Pacifiers will only be collected from children of that age group in order to restrict the common microbial flora found in a “well-baby” and thus likely to be found on the pacifiers in the study.

14)-If they say yes, have them sign the informed consent form/survey form for pacifier donors and complete the survey.

15)-Write on cup/bag “Latex” if the pacifier is latex or write “Silicone” if the pacifier is silicone. Also write the subject number on the cup/bag to match the form with the pacifier.

16)-Give participant a brand new pacifier to replace the old one (silicone or latex depending on the type donated for the project).

17)-Open the cup/bag for pacifier.

18)-Have participant put used pacifier in bag/cup.

19)-Close sterile bag/cup.

20)-Remove gloves and dispose in mall garbage container.

21)-Put on a new pair of gloves.

22)-Repeat steps 11 - 20 with 17 additional parents and pacifiers (or additional parents if the correct number of pacifiers of each type are not collected).

23)-Put all latex sealed bags/cups into two large Ziploc storage bags.

24)-Label these bags “Latex Pacifiers.”

25)-Obtain two more Ziploc bags.

26)-Label this bag “Silicone Pacifiers.”

27)-Put all silicone pacifiers into bags.

PART 2 (conducted at laboratory)

28)-Travel with qualified scientist to lab.

29)-Prepare to do laboratory work by putting hair up, putting on a lab coat, washing hands, putting on safety goggles, and putting on sterile latex gloves.

30)-Sample 4 latex pacifiers (1 unsucked control, 3 sucked) and 4 silicone pacifiers (1 unsucked control, 3 sucked) with a sterile swab. Rub the head of the swab on the nipple of the pacifier. Put on a new pair of gloves between each sampling to prevent cross-contamination.

31)-Put swabs back into sterile package.

32)-Obtain and label 8 prepared petri dishes using the permanent black marker.

  • a)-dish 1 - “Control - Latex pacifier #1 no cleaning”
  • b)-dish 2 - “Latex pacifier #2 no cleaning”
  • c)-dish 3 - “Latex pacifier #3 no cleaning”
  • d)-dish 4 - “Latex pacifier #4 no cleaning”
  • e)-dish 5 - “Control - Silicone pacifier # 1 no cleaning”
  • f)-dish 6 - “Silicone pacifier #2 no cleaning”
  • g)-dish 7 - “Silicone pacifier #3 no cleaning”
  • h)-dish 8 - “Silicone pacifier #4 no cleaning”

33)-Put on fresh pair of gloves.

34)-Remove the swab from package and transfer sample to agar on dish 1 by dragging the swab across the agar several times while turning the swab.

35)-Use tape to seal petri dishes (not to be opened). Bring completed petri dishes to incubator.

36)-Place dishes on shelves in 37 degrees Celsius incubator.

37)-Incubate for 48 hours.

38)-On collection day two, if sufficient specimens were not obtained (9 of each type - latex, silicone), travel to a different mall with qualified microbiologist.

39)-Repeat steps 7 - 27 at second collection site (if necessary). If additional specimens are obtained, repeat steps 28 - 38 at laboratory before moving on to step 40.

40)-Approximately 48 hours after beginning incubation, travel with qualified scientist to lab.

41)-Prepare to do laboratory work by putting hair up, putting on a lab coat, washing hands, putting on safety goggles, and putting on sterile latex gloves.

42)-One by one, carefully remove sealed petri dishes from incubator without removing the lid.

43)-Store in refrigerator at 6 degrees Celsius.

PART 3 (conducted at laboratory)

44)-Dispose of gloves and put on a new pair.

45)-Obtain a clean 3 quart saucepan.

46)-Fill it up with 1 quart of distilled water.

47)-Bring the water to a boil on portable burner in laboratory.

48)-Take one latex pacifier that was in a bag/urine cup and put the pacifier in the boiling water for 5 minutes. Carefully submerge pacifier in water.

49)-After 5 minutes, carefully take out the pacifier from the water using metal tongs and place in fresh sterile bag.

50)-Repeat Steps 46 - 49 with three more latex and silicone pacifiers (1 unsucked and 3 sucked of each type).

51)-Turn off burner/stove.

52)-Pour water in pot down the drain in the lab.

53)-Open a swab package and take out sterile swab.

54)-Sample each of the 8 sterilized pacifiers (1 unsucked control and 3 sucked pacifiers of each type) by rubbing the head of the swab on the pacifier.

55)-Return each swab to package.

56)-Return each pacifier back into sterile bag and put it to the side.

57)-Obtain and label 8 petri dishes

  • a)-dish 9 - “Control - Sterilized latex pacifier #1.”
  • b)-dish 10 - “Sterilized latex pacifier #2.”
  • c)-dish 11 - “Sterilized latex pacifier #3.”
  • d)-dish 12 - “Sterilized latex pacifier #4.”
  • e)-dish 13 - “Control - Sterilized silicone pacifier #1.”
  • f)-dish 14 - “Sterilized silicone pacifier #2.”
  • g)-dish 15 - “Sterilized silicone pacifier #3.”
  • h)-dish 16 - “Sterilized silicone pacifier #4.”

58)-Put on fresh pair of gloves.

59)-Obtain dish 9 - “Control - Sterilized latex pacifier # 1.”

60)-Take out one unsucked, latex pacifier which was sterilized.

61)-Transfer sample to agar on dish 9 by dragging the swab across the agar several times while turning the swab.

62)-Dispose of swab properly in the medical waste disposal bag.

63)-Repeat steps 58 - 62 using dishes 10 - 16.

64)-Dispose of gloves and put on a new pair.

65)-Use tape to seal petri dishes (not to be opened). Once all petri dishes are prepared, put the 8 dishes in incubator for 48 hours at a temperature of 37 degrees Celsius.

66)-Properly dispose of gloves and cups / bags that the pacifiers were in (in laboratory medical waste disposal bags).

67)-After 48 hours, travel with qualified scientist to lab.

68)-Prepare to do laboratory work by putting hair up, putting on a lab coat, washing hands, putting on safety goggles, and putting on sterile latex gloves.

69)-Carefully remove all 8 sealed petri dishes from incubator without removing the lids.

70)-Store in refrigerator at 6 degrees Celsius (now dishes 1 - 16 are in the refrigerator).

PART 4 (conducted at laboratory)

71)-Dispose of gloves and put on a new pair.

72)-Obtain and label 8 prepared petri dishes using the permanent black marker.

  • a)-dish 17 - “Control - Latex pacifier #1 hand washed”
  • b)-dish 18 - “Latex pacifier #2 hand washed”
  • c)-dish 19 - “Latex pacifier #3 hand washed”
  • d)-dish 20 - “Latex pacifier #4 hand washed”
  • e)-dish 21 - “Control - Silicone pacifier # 1 hand washed”
  • f)-dish 22 - “Silicone pacifier #2 hand washed”
  • g)-dish 23 - “Silicone pacifier #3 hand washed”
  • h)-dish 24 - “Silicone pacifier #4 hand washed”

73)-Move dishes to the side.

74)-Obtain a control, unsucked latex pacifier.

75)-Wash the pacifier under warm running water, with liquid dish soap, for 5 seconds.

76)-Obtain a paper towel and dry the pacifier.

77)-Open sterile swab in package.

78)-Sample the latex pacifier by rubbing the head of the swab on the nipple of the pacifier.

79)-Put latex pacifier back into cup/bag and put it to the side.

80)-Transfer sample to agar on dish 17 by dragging the swab across the agar several times while turning the swab.

81)-Put lid onto the dish and seal with tape (not to be opened).

82)-Move dish 17 to the side.

83)-Dispose of swab properly in the medical waste disposal bag.

84)-Dispose of gloves and put on a new pair.

85)-Repeat steps 74-84 with dishes 18 - 24, with the appropriate specimen type or control.

86)-Dispose of all sampled pacifiers in the medical waste disposal bag.

87)-Once all dishes are inoculated, carefully, one by one, transfer all 8 sealed dishes to the incubator for 48 hours at a temperature of 37 degrees Celsius.

88)-After 48 hours, travel with qualified scientist to lab.

89)-Prepare to do laboratory work by putting hair up, putting on a lab coat, washing hands, putting on safety goggles, and putting on sterile latex gloves.

90)-Carefully remove all 8 sealed petri dishes from incubator without removing the lids.

91)-Store in refrigerator at 6 degrees Celsius (now dishes 1 - 24 are in the refrigerator).

PART 5 (conducted at laboratory)

92)-Travel with qualified scientist to lab.

93)-Prepare to do laboratory work by putting hair up, putting on a lab coat, washing hands, putting on safety goggles, and putting on sterile latex gloves.

94)-Remove dishes 1 - 24 from refrigerator.

95)-Transfer dish 1 to laboratory table.

96)-Look into the petri dish, keeping it closed and sealed. Count all the colonies of bacteria using the grid lines on the petri dish. Record. Calculate the percentage of grids occupied by microbial growth on the dish.

97)-Record additional observations regarding the appearance of the sealed dish.

98)-Try to determine the types of bacteria within the dish by using Bergey’s Manual for Identifying Bacteria.

99)-Record any additional observations.

100)-Repeat steps 95 - 99 with dishes 2 - 24.

101)-When done recording observations for all samples, seal the waste disposal bag and leave in lab for proper disposal.

102)-The means from each of 6 data sets (3 different treatment methods to each of 2 different types of pacifiers), will be analyzed by preparing a histogram display of the number of colonies present on each of the 6 data sets.

Step 6: Results

Trials 1 - 4 were conducted using latex pacifiers and no cleaning method. The percentage of petri dish grids filled by colonies (out of 32) on the control pacifier was 6.25%. The average percentage of petri dish grids filled by colonies (out of 32) on the pacifiers in the experimental group was 56.25%. Trials 5 - 8 were conducted using silicone pacifiers and no cleaning method. The percentage of petri dish grids filled by colonies (out of 32) on the control pacifier was 0%. The average percentage of petri dish grids filled by colonies (out of 32) on the pacifiers in the experimental group was 51.04%.

Trials 9 - 12 were conducted using latex pacifiers and the cleaning method of boiling, or sterilizing. The percentage of petri dish grids filled by colonies (out of 32) on the control pacifier was 0%. The average percentage of petri dish grids filled by colonies (out of 32) on the pacifiers in the experimental group was also 0%. Trials 13 - 16 were conducted using silicone pacifiers and the cleaning method of boiling, or sterilizing. The percentage of petri dish grids filled by colonies (out of 32) on the control pacifier was 0%. The average percentage of petri dish grids filled by colonies (out of 32) on the pacifiers in the experimental group was 0%.

Trials 17 - 20 were conducted using latex pacifiers and the cleaning method of hand washing using warm water and soap. The percentage of petri dish grids filled by colonies (out of 32) on the control pacifier was 0%. The average percentage of petri dish grids filled by colonies (out of 32) on the pacifiers in the experimental group was 2.08%. Trials 21 - 24 were conducted using silicone pacifiers and the cleaning method of hand washing using warm water and soap. The percentage of petri dish grids filled by colonies (out of 32) on the control pacifier was 0%. The average percentage of petri dish grids filled by colonies (out of 32) on the pacifiers in the experimental group was 41.67%. Overall, the average percentage of petri dish grids filled by colonies (out of 32) on the latex pacifiers was 19.44%, and the total average percentage of petri dish grids filled by colonies (out of 32) on the silicone pacifiers was 30.89%.

Step 7: Conclusion

***Spoiler Alert: Buy latex pacifiers and boil them!!!***

The results of this experiment did not support the hypothesis. It was hypothesized that silicone pacifiers would harbor less bacteria because they are more durable than latex. Because they are durable, it was believed that they would be more difficult to crack which means they would harbor less bacteria. After cleaning it in “a mother’s way” (handwashing with soap and warm tap water), and after boiling, it was hypothesized that silicone would still be cleanest because it began with less bacteria. Results of this experiment indicated that the best way of cleaning was boiling, or sterilizing, which was hypothesized, but in total, silicone pacifiers harbored the most bacteria.

I think the reason why I got these results was because when I was washing the silicone pacifiers with warm water and soap, I noticed that the water would stay inside of the silicone head of the pacifier, and it would not come out. This could have been a place where a lot of bacteria was because this part was not cleaned very well. This could have affected the results. Another reason latex pacifiers were cleaner could have been because some of the latex ones were only used for a couple of days, unlike the silicone ones which were used much longer. Because they were used for a shorter period of time, less bacteria could have been on the pacifier. This could have also affected the results of this experiment.

When I got the results of this experiment, I was very surprised that I found that the latex pacifiers harbored less bacteria than the silicone ones. I was almost sure that the silicone pacifiers would be the most hygienic. I was also surprised that I found that a silicone pacifier used since birth for two years did not have any visible bacteria on the petri dish. I am not sure of the reason, but it could be from the saliva. It is not proven yet, but saliva could be able to heal wounds. Researchers at the University of Florida have found that some properties in saliva helped heal a wound twice as fast. Maybe this could have been the reason that the pacifier did not have any visible bacteria.

If I could do this experiment again, I would want to be more accurate. I would want to get the same amount of silicone and latex pacifiers all used by infants of the same age and for the same amount of time. This would enable me to be sure on which type of pacifier harbors the least bacteria. I would also want to find out what types of bacteria are on the pacifiers and see which brand might have the most bacteria. Unfortunately, I was unable to determine the types of bacteria on the pacifiers. This experiment also led me to wonder if pacifiers bought from different stores would cause them to have different levels of bacteria. Maybe in another experiment, I could see if this is actually true.

This experiment could help others because it shows parents that latex pacifiers are better for their infants. When I was collecting pacifiers from people, I noticed that a majority of the people used silicone and not latex pacifiers. I also found that when I was buying pacifiers to give to people in return, the latex pacifiers were a lot cheaper than the silicone ones. This experiment concludes that latex pacifiers have less bacteria, so parents should have their infants use them because of these reasons. If infants start to use latex pacifiers instead of silicone ones, this may be able to reduce the number of times they get sick. This experiment could also help the companies who make the pacifiers because it shows that the latex ones are more hygienic.

<p>Well written!</p><p> I'd be interested in knowing what (if any) types of bacteria are present on the pacifiers straight out of the package, prior to and after washing.</p><p> You make mention of bacteria identification. Were you able to identify any (I may have missed that part)?</p><p> I think it's also important to note that not all bacteria are harmful to health. Is there also the possibility that there is a difference in the types of bacteria each pacifier harbors? Is there a &quot;preference?&quot; Again, the implication is the level of risk.</p><p> I'm also curious what research you reviewed. Blogs, websites, peer-reviewed research articles published in reputable scientific journals, etc.</p><p> And finally, tell us a bit about yourself (no personal info necessary). Was this for a class? What level?</p><p>Thanks.</p>
<p>Thanks! </p><p>I did this project for a science fair last year when I was in 8th grade. Unfortunately, I was unable to identify any types of bacteria present because, since I was in 8th grade and not in a high school level category yet, the rules prevented me from actually identifying the types.</p><p>And yes, you make a good point that not all bacteria are harmful to health and that it's possible that there's a difference in the bacteria on the pacifiers; however, in this project, I was just seeing which held more bacteria. In the future, if I continue this project, I really want to actually see which types of bacteria are on the pacifiers.</p><p>Also, I attached a PDF of the research I did beforehand. At first, I was going to do this project to see if there were infection-causing bacteria on pacifiers, so there might be some research on that, too. It is pretty long, though (you might not want to read the entire thing :) ).</p>
<p>Thanks for your reply. I'm very impressed! I think I counted sixteen references, and most of the papers I wrote during graduate school (social work) only required around ten. Other differences aside (I was writing three or so papers every three weeks or so), I really had no idea this work was of eighth grade level. Well done!</p><p>BTW-Love the cat pic. I also have a tabby with similar markings He's a GOOD kittie!</p>
<p>Thank you so much!</p>
<p>Excellent initiative! Thanks for sharing it.</p>
<p>Thank you!!</p>

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