Questions about growing Streptococcus Mutans

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brandimiller610
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Re: Questions about growing Streptococcus Mutans

Post by brandimiller610 »

Sounds great! Best of luck with your project!
phanithans
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Re: Questions about growing Streptococcus Mutans

Post by phanithans »

Hello again! I have more questions about my project now. I hope you can answer them.

1. I was originally planning on using a selective growth medium to grow the bacteria I am using in my experiment, Streptococcus Mutans and Lactobacillus Acidophilus (MSAT Agar for Streptococcus and MRS Agar for Lactobacillus Acidophilus). Unfortunately, I am unable to easily source a selective medium for Streptococcus Mutans. Is there another selective medium that I can find easily, or can I use normal nutrient agar for both species?

2. My project is about the effect of copper water on already present and growing oral bacteria (Bactericidal, not bacteriostatic). Would the zone of inhibition test give me relevant results, or should I use another test? If so, what test should I use? My plan was to grow the bacterial lawn, then put down disks impregnated with copper water if I couldn't do a conventional zone of inhibition test. Would this work?

I probably have more questions coming soon! Thank you so much!
brandimiller610
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Re: Questions about growing Streptococcus Mutans

Post by brandimiller610 »

1. Blood agar is commonly used for growing streptococci. Columbia blood agar would work, or you could make tryptic soy agar (TSA) and add 5% sheep RBCs to make blood agar plates. This paper also compares multiple medias used to cultivate Streptococcus mutans and reports the efficiency of each one: https://pubmed.ncbi.nlm.nih.gov/12035953/. It looks like you have access to MRS -- this is the best selective media for lactobacilli. If you don't have access to MRS, nutrient agar + glucose might work, but the lactobacilli would not grow as well, if they grow at all.

2. The disc-diffusion assay is testing the bacteriostatic properties of the copper water, rather than the bactericidal properties. To determine bactericidal properties, you should determine the minimum inhibitory concentration (MIC) of the bacteria (i.e. the minimum concentration of copper necessary to inhibit bacteria growth). You could also determine the minimum bactericidal concentration (MBC), which is the drug concentration resulting in a 1000x reduction in bacterial density. More information can be found here: https://www.idstewardship.com/basics-ba ... ntibiotics and https://pubmed.ncbi.nlm.nih.gov/11420333/. Determining the MIC tells you at what minimum concentration copper is bactericidal to your strains.

Hope this helps!

--Brandi
phanithans
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Re: Questions about growing Streptococcus Mutans

Post by phanithans »

Thank you for your help! I now have another question. I tried to find MRS Broth online, but I was unable to find a site where I could buy just a small amount of broth (all of the sites were selling in bulk). Do you know where else I can buy a small amount of broth (about 5 ml) or if I can use another method to rehydrate the lyophilized lactobacillus?

Thanks you again in advance!
brandimiller610
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Re: Questions about growing Streptococcus Mutans

Post by brandimiller610 »

Hi again,

Keep in mind that you will need MRS powder to make both broth and agar (unless you are using pre-made plates). So you will need a larger quantity. Vendors like Sigma-Aldrich and FisherScientific sell MRS in 500 g amounts -- I am fairly sure this is the smallest amount sold in one container.

However, if you want to try a different medium to rehydrate your L. acidophilus, check out this paper: https://www.ncbi.nlm.nih.gov/pmc/articl ... 56/?page=2. It looks like Ringer solution and even water had decent cell survival, along with MRS. I am not sure what reagents you have access to, but I hope this helps! If you rehydrate the pellet in water or Ringers, I think then you would be able to directly inoculate onto MRS plates. Unfortunately, I do not have much experience using lyophilized bacteria -- I use frozen glycerol stocks.

Hope this helps!

--Brandi
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