v Principle:- 

               When sulfur-containing amino acids are decomposed by the enterobacteria, hydrogen sulfide is                           produced. It reacts with ferrous ions and the formation of ferric sulfide imparts a black color to the                   medium.

    v Requirements:-

           1.      TSI medium

        v Procedure:-

1.      Stab the butt and streak the slant at 37°C

2.      Observe daily for seven days for blackening caused by H,S.

    v    Results:-

                  1.           Blackening: Positive test.

                     2.           No blackening: Negative test,No HS production.

               v Quality control:-

Use following microorganisms to confirm the reliability
of reagents:

Positive control: Staphylococcus aureus

Negative control: Escherichia coli