Can a mixed culture be used to inoculate TSI slant?

Can a mixed culture be used to inoculate TSI slant?

So the medium must be inoculated with a pure culture, often an isolated colony from another identification medium, and there will not be any useful information if it is inoculated with a mixed culture. Do not use an inoculating loop to inoculate a tube of Triple Sugar Iron Agar.

Why sucrose is added in TSI?

Why Sucrose is added in TSI? Addition of sucrose in TSI Agar permits earlier detection of coliform bacteria that ferment sucrose more rapidly than lactose. Adding sucrose also aids the identification of certain gram-negative bacteria that could ferment sucrose but not lactose.

How do you make agar TSI?

Preparation of TSI agar medium

1. Combine the ingredients, and adjust the pH to 7.3.
2. Boil to dissolve the agar and dispense into tubes.
3. Sterilize by autoclaving at 121°C for 15 minutes.
4. Cool in a slanted position to give a 2.5 cm butt and a 3.8 cm slant.

What color is TSI Agar?

Fermentation reactions are read on the slant and in the butt, with a color change from red (alkaline) to yellow (acid). The dextrose concentration in TSI Agar is one-tenth the concentration of lactose and sucrose.

How do you make a TSI slant?

Method

1. With a straight inoculation needle, touch the top of a well-isolated colony.
2. Inoculate TSI by first stabbing through the center of the medium to the bottom of the tube and then streaking the surface of the agar slant.
3. Leave the cap on loosely and incubate the tube at 35°-37°C in ambient air for 18 to 24 hours.

How do you read a TSI?

TSI Agar must be read within the 18-24 hour stated incubation period. A false-positive reaction may be observed if read too early. A false-negative reaction may be observed if read later than 24 hours. An organism that produces hydrogen sulfide may mask acid production in the butt of the medium.

What does Triple Sugar Iron test for?

Triple sugar iron agar, or TSI, is a differential medium that tests a bacterial strain for several different properties at once. It tests for acid and gas production from the fermentation of glucose and sucrose and/or lactose and for the production of hydrogen sulfide.

How do you read TSI results?

Triple sugar iron agar (TSI) is a differential medium that contains lactose, sucrose, a small amount of glucose (dextrose), ferrous sulfate, and the pH indicator phenol red….