Triple Sugar Iron (TSI) agar slant

Hello Eveyone
Today's media which will be made easy is TSI media.

TSI Media as the name suggests has three types of sugars:

Lactose - 1%
Sucrose - 1% 
Glucose - 0.1%

One way that I use to remember this is:  'g' in glucose as a 0 looking like figure, hence this is the one with 0.1% concentration.

Purpose:
It is basically used to differentiate between gram negative organisms especially Enterobacteriacae. 
This differentiation is based on the differences in carbohydrate fermentation patterns and hydrogen sulfide production by the various groups of intestinal organisms.

Indicator - Phenol red (though the color of the medium is orange)

Acidic conditions - orange to yellow.

Alkaline conditions - orange to deep red or pink.

The media is made in slightly slanting position, to yeild more surface area of slant as well as butt. the slant surface is streaked with the loop, whereas the butt is stabbed with a straight wire.

Sodium thiosulphate, ferrous sulphate and ferrous ammonium sulphate indicate the presence of H2S production.

Glucose utilizing organisms will produce low amounts of acids which oxidizes within 24 hours and reverts back to orange color or pink color in the slant.

Anaerobic organisms grow in the butt region of the medium and use thiosulphate as an electron acceptor, thus producing H2 gas which causes bubbles in the butt or sometimes elevates the entire slant.

That's all.

Hope it helps.

Lots of love

-Staph <3