Bacteria in restaurants

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Bacteria in restaurants

Postby bsec3045 » Thu Sep 19, 2013 2:27 pm

I am choosing a topic for my 8th grade honors science fair and have a few questions.

I was thinking about comparing food trays, at five fast food restaurants, to see which is the "cleanest/dirtiest". I know bacteria can be difficult to identify, outside of a lab, so should I keep it simple and not attempt to identify any of the samples? I'm thinking that I would take a swab on a tray at each restaurant, then clean the same area with an alcohol swab and re-swab (to have a controlled variable). Each would be in a petri dish (agar) so...10 dishes. What's the best way to state this? Should it only be looking for bacteria growth...the amount? I'm interested in this idea but am not quite sure the best approach. Would it be better to compare the trays to another item in each restaurant, like the bathroom faucet or door handle?

I appreciate any help you might be able to provide.
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Re: Bacteria in restaurants

Postby tchoate » Thu Sep 19, 2013 5:38 pm

Hello,
This is a very interesting idea for an experiment. You are on the right track with the idea that you would want to measure growth, NOT attempt to identify the organisms. That Is an advanced and potentially dangerous concept. For a control you can use simply an un- inoculated agar plate which should show zero growth . What you may need to consider is if you are measuring how clean the restaurant is, are you taking samples right after they have been washed or after people have used them? One is not the measure of the restaurant but the customers. Of course if the employees "wipe" the trays down , then you have a cleanliness issue to deal with.

To figure out the cleanest restaurant compare one variable against each other, if the trays are to variable pick another area. You may even consider comparing for instance, bathrooms in different types of facilities. Like restaurants, fast food, clothing stores, coffee shops etc. to see what type of establishment is cleanest. Just an idea.

If you stay with the trays;
Figure out which state the trays are in when you measure the growth, this will guide you to your hypotheses . Then the growth is measured by counting colonies growing on the plates.

Follow up with me if you have any questions.

Good Luck,

T.choate
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Re: Bacteria in restaurants

Postby bsec3045 » Fri Sep 20, 2013 10:55 am

I was thinking my samples will be taken once the tray is given to me (which one would assume should have been cleaned in between each customer). I guess it could be more of "how much bacteria is on your food tray?" I plan to find out each restaurants policy of cleaning their serving trays as well as research the product material of the trays (the type of plastic) and how it relates to bacteria. I know certain surfaces are more likely to "keep" bacteria on them. I could actually do a cleaning product (lysol wipe, disinfectant etc.) for the second swab (controlled variable) to see how effective that product is at disinfecting. Is that too much? Do you think I should keep it to one subject?

Thanks for your help!
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Re: Bacteria in restaurants

Postby tchoate » Fri Sep 20, 2013 3:09 pm

This sounds like a good idea as long as their cleaning method is fairly similar because then you introduce another variable of
" which cleaning method is better" , in addition to which trays are the cleanest. Of course that could be an additional second hypothesis if you wanted. As far as the second wipe with a disinfectant, this assumes zero growth as a control but it might surprise you that you still may have bacterial growth and that you are comparing how well the disinfectant works, thereby indirectly measuring how dirty the trays still are. You see disinfectants don't work instantly which is a common misconception, but need what is called " contact" time to truly work. So decide what your variable or variables actually are, you may have more than one, and this should help you pick your control.

Good luck,
Hope this helps...

Let me know how you are doing

T. Choate
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Re: Bacteria in restaurants

Postby bsec3045 » Fri Sep 20, 2013 6:17 pm

Ok, I'm thinking that could get tricky but I will see if I can identify the exact cleaning method at each restaurant. I might need to just keep it to whether or not bacteria is present on the tray because I was always intending to sample a tray that is "given" to me as a customer, as a "clean" tray. Wouldn't that be what I could do and not introduce the cleaning method...like the idea of the door knobs at different types of places that you mentioned earlier. I wouldn't necessarily know how they are cleaned or how often. I would rather have a tray that they don't know I'm sampling. Of course they would heavily clean the tray if they know I'm going to swab it. So, I like the idea of getting what's really on the tray. I'm just trying to hurry up and narrow things down because I need to do my research paper and references.

I might think about the idea of the bathroom door knob at different types of places...could be interesting!
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Re: Bacteria in restaurants

Postby tchoate » Fri Sep 20, 2013 7:15 pm

Hello,
Yes, I did not want to complicate things for just give you something to consider that may be a variable. The idea of " how clean is my tray" from a customer point of view is interesting and perhaps " scary" if you think about it. I think you have a good grasp on what you want to do and how to proceed. Swabbing the trays to a plate for your tests, will give you a good idea of cleanliness like you mentioned.

The bathroom knobs etc. is promising also if you having trouble with the trays.

Great job with your idea. Good luck.
Let me know how your research is going.

T.choate
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Re: Bacteria in restaurants

Postby bsec3045 » Sat Sep 21, 2013 8:22 am

Thanks so much for your help...I will keep you posted and definitely ask for advice if I run into any problems.
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Re: Bacteria in restaurants

Postby bsec3045 » Sat Sep 21, 2013 9:26 am

I forgot to ask...can I name the restaurants in the project or should I say restaurant A, B, C, D & E?
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Re: Bacteria in restaurants

Postby tchoate » Sat Sep 21, 2013 11:24 am

I think it would be best to stick with the letter naming just for ethics. However, in your lab notebook keep a record of which is which so if anyone asks you could reveal the information. You may want to check the science buddies forum to see if there is a specific rule about this.

Glad to help.

Looking forward to your results.

Lots of luck.

T. Choate
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Re: Bacteria in restaurants

Postby bsec3045 » Sun Sep 22, 2013 5:34 pm

I have questioned the managers at the restaurants and they all have similar cleaning methods...it will be interesting to see what the samples actually show, and to see how much bacteria actually grows from each of the five tray samples. None of the restaurants knew the manufacturer of their trays, and only one stated that Microban was in their trays. Honestly, I don't think they know where the trays came from or the material they are made of. I mentioned Microban in my research as a material which helps reduce bacteria growth in plastics.

When I take the samples from each tray should I just use a sterilized cotton swab? Does it need to be moistened in any way since the trays will be dry? Or do I swab straight on the tray with a dry swab? I will immediately transfer this to the agar petri dish but I wanted to be sure of the best method for swabbing. I do still plan to do a second swab after using Lysol to see the difference in the two samples.

Also, do my blood agar petri dishes need to remain refrigerated until I use them? Thanks again for any helpful advice!
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Re: Bacteria in restaurants

Postby tchoate » Sun Sep 22, 2013 7:32 pm

Hello,
First off yes, you must keep your plates refrigerated until you use them or the will most likely become contaminated. Also, on this note make sure when you incubate them they are upside down, in other words the top is face down or else condensation will form on the lid and drip onto the agar and interfere with growth. As far as swabbing it will be best to use a moist swab or else transfer will be difficult and samples will be hard to collect. You could just use distilled water to moisten your swabs ( or deionzed) like contact lens solution or you can buy distilled water, NOT spring water or drinking water. These types of water should be bacteria and contaminant free. Make sure your swabs are moist enough not dripping wet.

I don't know that the Lysol is necessary unless you are actually conducting two experiments. This is actually a second test. But that is fine if you choose to do it that way.

Make sure you have a control ( such as a plate that is not inoculated). As Lysol would not be a control but a test.

Good luck sounds like you have a good grasp on things !!!

T. Choate
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Re: Bacteria in restaurants

Postby bsec3045 » Sun Sep 22, 2013 7:53 pm

Great, thanks! That is how I have the agar plates now. I will be sure to use the distilled water when sampling and will have a control petri dish for each tray (no sample in it). I think I will skip the Lysol and keep it to the 10 petri dishes...5 with samples, 5 as controls. I really appreciate your help...thank you!
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Joined: Wed Sep 18, 2013 5:17 pm
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Project Due Date: October 1, 2013
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Re: Bacteria in restaurants

Postby bsec3045 » Tue Oct 01, 2013 6:21 pm

I am not sure how to write the variables (independent, dependent & constant) for this. Are the independent: the 5 restaurants, 5 food trays, distilled water, sterilized cotton swabs & agar petri dishes? Dependent: the amount of bacteria that grows from each tray sample. Constant: Should this be the same as the independent??? Thanks!!
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Joined: Wed Sep 18, 2013 5:17 pm
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Project Question: How much bacteria...
Project Due Date: October 1, 2013
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Re: Bacteria in restaurants

Postby JMP » Wed Oct 02, 2013 10:33 am

Your independent variable is the factor that you are changing in the experiments, so you are correct that it would be the restaurants, because you are changing which restaurant each tray is from. This does not include things like distilled water, cotton swabs, and petri dishes. Those would be closer to controls, or controlled variables, which the investigator keeps constant throughout. In your case that would tend to be the area of each tray swabbed, the amount of time and the temperature you let the petri dishes grow at, etc. Those could include the cotton swabs, type of petri dishes, and distilled water, etc. The dependent variable is the variable that you do not control, so again, you are correct that this would be the amount of bacteria that grew.
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Re: Bacteria in restaurants

Postby bsec3045 » Tue Oct 22, 2013 1:20 pm

I took my petri dishes to the school lab this morning, for my experiment. How long should I leave them there for the bacteria to grow? Thanks!
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