Science Buddies: "Ask an Expert"

I am interested in the antibiotic and anti-fungal effects of saliva on skin diseases. I just have a few questions. I plan on using agar plates and purchasing the Staphylococcus epidermidis and Candida Albicans from a scientific company. I will make my bacteria lawn from this. I wanted to use some commonly used skin ointments to compare it to the human saliva. Now for the questions...
1. I wanted to use the Kirby Bauer method but ointments will not be absorbed by the sterile disks, right?
2. If I am right about question 1 how would I apply the ointments? Would I directly apply it to the agar with a sterile swab? And when...At the time of incubation because rules of my science fair state that once the bacteria is incubated I can not reopen the petri-dishes.
3. Imagej software...I am not familiar with it but could possibly learn about it because it might be a better way to enumerate the bacteria and might be better way to have more data points. This is not my original idea I found this project online and the previous scientist used imagej.
4. Last year I did a microbiology project and made it all the way to my state science fair, but others in the microbiology category seemed to have better pictures, and testing methods, I will be doing this at my home but observing safe lab procedures. My teacher, while enthusiastic about the science fair does not give any additional help, so any advice you might give would be of great help.

Preppypaisley wrote:I am interested in the antibiotic and anti-fungal effects of saliva on skin diseases. I just have a few questions. I plan on using agar plates and purchasing the Staphylococcus epidermidis and Candida Albicans from a scientific company. I will make my bacteria lawn from this. I wanted to use some commonly used skin ointments to compare it to the human saliva. Now for the questions...
1. I wanted to use the Kirby Bauer method but ointments will not be absorbed by the sterile disks, right?
2. If I am right about question 1 how would I apply the ointments? Would I directly apply it to the agar with a sterile swab? And when...At the time of incubation because rules of my science fair state that once the bacteria is incubated I can not reopen the petri-dishes.
3. Imagej software...I am not familiar with it but could possibly learn about it because it might be a better way to enumerate the bacteria and might be better way to have more data points. This is not my original idea I found this project online and the previous scientist used imagej.
4. Last year I did a microbiology project and made it all the way to my state science fair, but others in the microbiology category seemed to have better pictures, and testing methods, I will be doing this at my home but observing safe lab procedures. My teacher, while enthusiastic about the science fair does not give any additional help, so any advice you might give would be of great help.

Hey Preppypaisley,

This sounds like such an awesome project (huge fan of microbio here)! I understand that you want to use the Kirby Bauer method, so if you needed to test skin ointments as well, I would either coat the disk in ointment (because it is correct that the skin ointment will not absorb well into the disk) or mix the ointment(s) with a bit of water, and then dip the disks into the ointment-water mix. The disks will be able to absorb the ointment this way, and you won't be breaking state rules by re-opening the petri dishes.
I wish I could help you with concern #3; however, I myself am not familiar with imagej. However, I'm sure many other fellow Experts would be knowledgeable about this program!
You seem to be careful about following all guidelines, which is awesome! I would just suggest handling the S. epi and C. albicans with great care (and perhaps parental supervision), since you're conducting this in your own home.
Good luck on this project, and if you have any more concerns, don't be afraid to ask more questions!

-JSK

Thank you JSK!!! I am working on my research paper today and it is very interesting but I am feeling overwhelmed.

I will be very careful! I will keep you updated on my decision to use imagej! I think this will just provide extra data for my project and I hope to use it but will need to figure it out.
Thanks again!

HELP!!!! I have attempted do the project but the Povidone Iodine I used stained the petri dish agar red and I can not really tell if there is a zone of inhibition present. I have found a white iodine that I have ordered but I am on a time crunch so I am not sure if it will get here in time.Also, my fungus is growing like gangbusters but my bacteria, Staph. Epidermidis is not growing. I do not have an incubator but have made a makeshift one.

Second question, is if I change my project do I have to soak antibiotic infused disks with water?

Preppypaisley wrote:HELP!!!! I have attempted do the project but the Povidone Iodine I used stained the petri dish agar red and I can not really tell if there is a zone of inhibition present. I have found a white iodine that I have ordered but I am on a time crunch so I am not sure if it will get here in time.Also, my fungus is growing like gangbusters but my bacteria, Staph. Epidermidis is not growing. I do not have an incubator but have made a makeshift one.

Second question, is if I change my project do I have to soak antibiotic infused disks with water?

Hey Preppypaisley,

For the iodine, I would suggest either getting another pair of eyes (perhaps a science teacher) to look at the petri dish and see if there is a zone of inhibition or not include the iodine as one of the skin ointments tested (since you're not sure if you'll get the iodine on time) and try to find a substitute skin ointment.
For the non-growing Staph. epi., there's a chance that your makeshift incubator might not have a high enough temperature, since Staph. epi's optimal temperature is 37 C, or 98.6 Farenheits.

For your second question, no, you do not have to soak anti-biotic infused disks with water. I just suggested water for ointments that were too solid to coat the disk.

Hope this helped, and sorry for not getting back to you sooner!

-JSK