TCBS Agar – Selective Agar For Vibrio Specie

 

Thiosulfate-citrate-bile salts-sucrose (TCBS) Agar is used in standard food testing methods and clinical specimen testing to isolate and detect Vibrio cholerae and Vibrio parahaemolyticus. Kobayashi developed TCBS agar by modifying Nakanishi's selective medium. This highly selective medium meets the nutritional needs of Vibrio species while also allowing them to compete with intestinal flora. This medium isolates the Vibrio species based on their ability to grow at an alkaline pH and high salt concentration. In cases of gastroenteritis caused by Campylobacter species, whose symptoms mimic those of cholera, the TCBS becomes extremely important. As no yellow bacterial growth is observed in the case of Campylobacter species on TCBS agar, the possibility of an incorrect diagnosis can be eliminated

Composition

Ingredients

Gm/L

Yeast extract

5.0

Proteose Peptone

10.0

Sodium thiosulfate

10.0

Sodium citrate

10.0

Ox gall

5.0

Sodium cholate

3.0

Saccharose

20.0

Sodium chloride

10.0

Ferric citrate

1.0

Bromothymol blue

0.04

Thymol blue

0.04

Agar

15.0

The incorporation of Ox gall, a synthetic occurring substance that suppresses primarily Enterococci, inhibits gram-positive bacteria. The selective agents are sodium citrate and sodium thiosulphate, which provide an alkaline pH to inhibit gram-positive organisms and suppress coliforms. The presence of sodium thiosulfate, in combination with ferric citrate, allows for the easy detection of hydrogen sulphide production. Saccharose (sucrose) is a fermentable carbohydrate that Vibrio species can use. The medium's alkaline pH promotes V. cholerae recovery while inhibiting the growth of others. As pH change indicators, thymol blue and bromothymol blue are included.

Principle

TCBS agar is selective as well as differential. Because of the presence of sucrose and dyes, it is highly selective and differential for Vibrio species. Acid is produced during the fermentation of sucrose, which converts the colour of bromothymol blue or thymol blue. When two dyes are used instead of one, the medium produces an array of yellow, green, or blue colours, allowing for differentiation between different Vibrio species. Nitrogenous compounds, vitamin B complex, and other essential growth nutrients are provided by proteose peptone and yeast extract. Bile, a bile salt and sodium citrate derivative, inhibits gram-positive bacteria and coliforms. Sodium thiosulphate is a good source of sulphur, which detects the production of hydrogen sulphide when combined with ferric citrate. Vibrio that can use sucrose will form yellow colonies. The pH indicators are bromothymol blue and thymol blue. The medium's alkaline pH promotes Vibrio cholerae recovery.

How To Prepare TCBS Agar?

  • In 1000 ml purified or distilled water, dissolve 89.08 grams of TM Media TCBS Agar.
  • To completely dissolve it, bring the medium to a boil.
  • Cool to 45–50 °C.
  • Mix well and pour into sterile petri plates.


Colony Characteristic

Microorganism

Colony Characteristic

Vibrio cholerae

Large yellow colonies

Vibrio parahaemolyticus

Colonies with blue to green centres

Vibrio alginolyticus

Large yellow mucoid colonies

Vibrio harveyi/Vibrio fischeri

Greyish-green to bluish-green colonies that show luminescence in the dark

Proteus/Enterococci

Partial inhibition. If growth occurs, colonies are small and yellow to translucent.

Pseudomonas/Aeromonas

Partial inhibition. Blue colonies if growth occurs.

At TM Media, we offer a wide range of culture media for bacterial or fungal isolation. Along with Culture Media, we also provide Laboratory Consumables, Biological Media Bases, Media Supplements, Antibiotic Sensitivity Discs, and many more.

For more, visit https://www.tmmedia.in/.

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