Dear first i would like to correct you that it is not nutrition broth rather it is Nutrient broth medium. Nutrient broth medium is a liquid medium without Agar which is used for inoculum preparation. While going for Disk Diffusion you have to prepare a solidified medium called Nutrient Agar Medium to check antimicrobial activity.                                    Please feel free for any assistance

Showkat Ahmad Ganie

Thank you so much 

that was so helpful 

Actually for Diffusion  Disk Test for antimicrobial activity Mular  Hinton Agar (MHA) medium is used and recommended rather than Nutrient agar medium. LB broth is usually used for inoculum preparation which is then smeared on MHA medium.

Dear Alham,

I endorse Showkat Ahmad Ganie.

Nutrient broth medium is a liquid medium without agar, that contains tryptone, yeast powder and other ingredients. Agar is a polysaccharide isolated from a plant and is used for microbial cultures on solid media. LB broth is generally used for inoculum preparation or start cultures in suspension medium.   

The only difference between broth and agar media is that broths do not contain an agar component...

For all the details refer to the link : http://www.ruf.rice.edu/~bioslabs/bios318/318manual.htm

Thank you.

There is only two difference between both

1. Agar is solidified media while broth is liquid media

2. Agar is used for the Isolation and preservation of bacterial culture while N. broth is used to prepare bacterial Culture for growth and cultivation for production.

All the answers are useful to understand the difference between broth and agar media.