Effect of juices on antibiotics

[ami123]

Experimenting on effect of juices on antibiotics. Using antibiotic disk available on school science supply store. Can adding the juice using cotton swab is enough or is there any other way to do the experiment? If we have antibiotic 500mg capsule, what concentration do we use to create water +antibiotic to make our own disk. Also, what concentration of juice and antibiotic mixture can be used?

[donnahardy2]

Hi Ami123,

Welcome to Science Buddies! This is a unique and really interesting science project idea! It sounds like you are doing a variation of this project idea, except you are using antibiotics instead of disinfectants.

http://www.sciencebuddies.org/science-f ... ml#summary

With a science project, you want to add a measured amount of your independent variable to the sample so that you will be able to get reproducible results. I suppose that you will be using the cotton swab to transfer the bacterial culture to the surface of the agar plate, so you could dilute the bacterial culture in the juice before using the cotton swab. You could dilute the culture 1:1 for a 50% juice sample and 1:1 with 50% juice for a 25% juice sample. Use water to dilute the control and keep all other experimental parameters controlled.

It's always a good idea to try 2-3 dilutions of your sample, but you might want to do a trial experiment with one plate divided in half, just to see what will happen before using all of your plates. This will give you a chance to adjust the experimental protocol, if necessary.

What antibiotics are your planning to use, and what type of juice samples? What information do you have on this topic from your background reading?

Donna Hardy

[ami123]

Thank you for responding. I was not thinking of using different concentration of the juice. Were thinking of using the antibiotic disk from carolina website Ampicillian 10mcg. Use that antibiotic disk and measure the inhibition Zone. Then on the disk, use cotton swab to transfer for different kinds of juices - grape fruit, crranberry juice, orange juice and green tea. Now thinking of it, not sure how much juice we are transfering and is hard to measure. Please advise as to this would work or not. This is last minute and we are getting materil tomorrow or wednesday and have to produce results early next monday.

Teacher also suggested a variation of this could be done, so can we use the 500mg of amoxicilin in different juice samples and measure it.?

Any help would be appreciated. any variation of it on E.coli is okay now as we have to make it wrk.

Also, without an incubator can we grow e.coli at home? If we have to create incubator like condition, how do we do it?

Once we culture it, can we use it grow in other petri dishes?

How long can we keep the culture we get from carolina website (155068) , so we do a trail and redo it.

Appreciate your help

[ami123]

Thank you for responding. I was not thinking of using different concentration of the juice. Were thinking of using the antibiotic disk from carolina website Ampicillian 10mcg. Use that antibiotic disk and measure the inhibition Zone. Then use different disks with jucices, r different kinds of juices - grape fruit, crranberry juice, orange juice and green tea and meaure the area.

Transfer using cotton swab the juice onto antibiotic disk and measure the inhibition area.

Now thinking of it, not sure how much juice we are transfering and is hard to measure. Please advise as to this would work or not. This is last minute and we are getting materil tomorrow or wednesday and have to produce results early next monday.

Teacher also suggested a variation of this could be done, so can we use the 500mg of amoxicilin in different juice samples. Any variation of it on E.coli is okay now as we have to make it wrk.

Also, without an incubator can we grow e.coli at home? If we have to create incubator like condition, how do we do it?

Once we culture it, can we use it grow in other petri dishes?

How long can we keep the culture we get from carolina website (155068) , so we do a trail and redo it.

Appreciate your helpami123

Posts: 2
Joined: Sun Dec 02, 2012 1:44 pm
Occupation: Student:10th grade.
Project Question: Effectiveness of juices on antibiotics
Project Due Date: December 12
Project Status: I am conducting my research

[donnahardy2]

Hi Ami,

Thanks for the additional explanation. I think I understand what you are doing now.

I recommend adding the juice directly to the antibiotic disc and letting it dry for a minute or two before applying it to the bacterial lawn before incubating the plate. Do you have access to a pipettor with sterile pipette tips? If so, I think you could pipette 20-25 uL of each juice onto a disc. If you don’t have pipettes, then use an eye dropper, or something similar, and add one drop of juice to each disc. One drop is equivalent to 20 uL (microliters), so this will give you a consistent volumne.

The bacteria that have been inoculated onto the surface of the agar will grow up overnight and you can see if there is a difference in the zone of inhibition between the control disc and the antibiotic plus juice discs.

Do you have a different antibiotic or bacterial culture to use? Amoxicillin is an antibiotic that inhibits the formation of the cell wall of Gram positive bacteria. E. coli is Gram-negative, so I don’t know how large the zones of inhibition will be with this combination. If you do not have any options, then proceed as you had planned since your project is due on Monday.

E. coli will grow at home at ambient temperature. Be sure to turn the plates upside down to avoid moisture condensation on the surface of the agar. It may take two days for the lawn to appear, since growth will be slower compared to an incubator at 37 degrees Centigrade. Can you set up the plates at school and seal them with parafilm and take them home? This would be the best way to handle this situation. It sounds like you do have your teacher’s permission to work at home, but normally you should do this type of experiment at school to comply with all science fair rules.

The culture from Carolina Biologicals should be transferred to new agar or broth to maintain it. The cells will die eventually, so you will want to transfer it to keep it alive. For your experiment, it would be best to grow up a new culture in broth for a few hours or overnight until the growth medium is very cloudy. This will give you a new culture in late log or early stationary phase that will be optimum for testing antibiotic sensitivity. You should transfer your stock culture about every two weeks and store it in the refrigerator

If you need more information, do check out the information on the Science Buddies website for information on microbiological techniques and storing bacterial cultures.

http://www.sciencebuddies.org/science-f ... ques.shtml

Please post again if you have more questions.

Donna Hardy

[ami123]

We are using amphicillin antibiotic disk. You mentioned about e.Coli being gram negative bacteria, which antibiotic works for e.coli the best. If one or two trails are shown friday, they might get next week to do some more trial. So, may be we can get one of those and test again. so please let us know.

Here are some of my questions
1.Once the bacterial culture tube is open can we close it and bring it home and how long will it stay. If the experiment has to be conducted again next week,can they use this bacteria and the pre made agar plates.
2.Can we store the agar plates and the bacteria in the refrigerator.

3.How long the agar and the pre made agar plates will last.

We do have tetracycline 500mg capsule. Would using 10ml of water to create the mixture be enough, so we could use it on blank disk , and also mix with this and use to test in a separate petri dish.

[donnahardy2]

Hi Ami,

You have very good questions.

Ampicillin is another variation of penicillin, so interferes with the formation of the cell wall for Gram-positive bacteria. Tetracycline interferes with the protein synthesis so is a general all-purpose antibiotic effective against a wide variety of bacteria. Tetracycline is more likely to be effective against E. coli, so would be a better choice for your experiment.

Here's a paper that reports the solubility of tetracycline in water at different temperatures. The temperatures are given in degrees Kelvin.

http://path.web.ua.pt/file/A56%20Varand ... rt%20I.pdf

Using the table, if the solubility of tetracycline is 17.8 mg/mL of water at 293 degrees Kelvin, how much water would you need to dissolve 500 mg of tetracycline at room temperature (about 20 degrees Centigrade)?

1, The time that the bacteria tube will stay alive depends the time from initial inoculation and incubation and on the storage temperature. You will be safe to assume that the E. coli would be alive for 2 weeks after initial inoculation, and possibly for 4 weeks in a sealed tube when stored between 2 and 8 degrees Centigrade. The culture should be transferred to new growth medium periodically to maintain culture viability.

2. Sterile agar plates should be stored upside down in the refrigerator in a sealed plastic bag. Once you have grown the bacteria on the plates, don't put them back in a refrigerator that has food stored in it. It's against lab rules to store bacteria cultures in a refrigerator that is used for food, but your tube culture would stay alive longer if you could keep it cold. Depending on your climate, you might be able to store the culture outside in a safe place if the temperature is cool, but not freezing. If you had a spare refrigerator available that did not have food stored in it, that would be perfect.

3. Premade agar plates will last for up to a week or two, but will not work if they dry out. Store the freshly made plates in a sealed plastic bag. If you are buying premade plates, use them as soon as possible.

Good luck! It sounds like you are set for a really great experiment. Let me know what happens.

Donna Hardy