Selective media

 Selective media :

* Selective media are the media which contain selective agents that permit growth of desired organism and inhibit growth of others.

* Examples of common selective media are azide blood agar, MacConkeys agar, deoxycholate citrate agar.

* For examples, addition of sodium azide at specific concentration into media inhibits gram negative bacteria and selectively allows growth of stapylococcus and streptococcus species.

* Mac Conkeys agar contains selective substance, the bile salt (sodium taurocholate), this substance inhibits growth of non intestinal organisms and allows growth of intestinal organisms.