Is ti big enough

[andweav]

I am testing garlic against antibiotics ability to kill bacteria.

My question is: Is a 6mm difussion disc big enough to kill enough bacteria to measure. I am using 100mm petri dish and want to test one per dish.
I am using the lawn method of growing bacteria.


Thanks for all the help!

[kerrmyau]

Hi andweav,

I am very interested in your topic and think it would make a great project.

The size of the ring formed is largely depended on the concentration of the antibiotic agent(s) in your samples, not the size of the disc used. So, it is important to run a series of standard with various known concentrations of antibiotics. This would be your positive control as well as your standard curve. The higher the standard concentration, the larger the clear ring formed around the disc.

By measuring the size of the ring formed on your unknown (in this case garlic) samples, you would be able to estimate the strength of the antibiotic substance found in garlic with respect to that of your standard. Just be consistent on the size of the disc, then your result can be easier to interpret. Of course, it is important that the disc cannot be too large that you cannot fit all of your samples in one single plate.

Let me know how it goes.

Kerrm