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. It is used to differentiate enterics based on the ability to reduce sulfur and ferment carbohydrates.
What is the purpose of TSI Agar?
TSI Agar is used for the differentiation of gram-negative enteric bacilli based on carbohydrate fermentation and the production of hydrogen sulfide. TSI Agar is used for the determination of carbohydrate fermentation and hydrogen sulfide production in the identification of gram- negative bacilli.
What is the principle of TSI?
Principle of TSI test: The presence of fetrous sulphate and sodium thiosulphate fulfills the demand of sulphur and there is the indicator phenol red for the indication of change in the invironment of the media due to the production of acid or alkali.
What is the purpose of TSI test and what are Enterobacteriaceae?
The test is used primarily to differentiate members of the Enterobacteriaceae family from other gram-negative rods. It is also used in the differentiation among Enterobacteriaceae on the basis of their sugar fermentation patterns.
How do you interpret agar TSI?
Expected results of TSI Agar test are:
- Alkaline slant/no change in butt (K/NC) i.e Red/Red = glucose, lactose and sucrose non-fermenter.
- Alkaline slant/Alkaline butt (K/K) i.e Red/Red = glucose, lactose and sucrose non-fermenter.
What are the main components of the TSI media?
The TSI slant is a test tube that contains agar, a pH-sensitive dye (phenol red), 1% lactose, 1% sucrose, 0.1% glucose, and sodium thiosulfate and ferrous sulfate or ferrous ammonium sulfate. All of these ingredients are mixed together, heated to sterility, and allowed to solidify in the test tube at a slanted angle.
What three sugars are used in the TSI Agar?
TSI Agar contains three carbohydrates dextrose, lactose and sucrose. A color change from a reddish salmon to a pale yellow indicates carbohydrate fermentation; this acid production is detected by the Phenol Red pH indicator.
What is the purpose of carbohydrate fermentation test?
The carbohydrate fermentation test is used to determine whether or not a bacteria can utilize a certain carbohydrate. It tests for the presence of acid and/or gas produced from the fermentation of a single particular carbohydrate.
What genus of bacteria is suggested by your TSI Agar?
Hardy Diagnostics Triple Sugar Iron (TSI) Agar is recommended for use in the differentiation of Enterobacteriaceae by their ability to ferment glucose, lactose, and sucrose, and their ability to produce hydrogen sulfide.
Why is there more lactose and sucrose than glucose in TSI Agar?
Since lactose and sucrose are present in much higher concentrations than glucose, acid formation in the butt is due to these sugars, while the acid formation from glucose is suppressed by a rapid oxidation of the small amount of acid in the slanted area of the tube, resulting in a neutral or alcaline pH reaction when
What is on the TSI test?
The TSI exam covers 4 different sections – mathematics, reading, writing, and an essay section. The TSI exam consists primarily of multiple choice questions.
What does a a mean in TSI?
Summary of Possible TSI Reactions K = alkaline = Red; A = acid = Yellow; NC = No change; G = gas produced; H2S = hydrogen sulfide produced.
Why is glucose added to lysine iron agar?
Lysine iron agar contains lysine, peptones, a small amount of glucose, ferric ammonium citrate, and sodium thiosulfate. When glucose is fermented, the butt of the medium becomes acidic (yellow). If the organism produces lysine decarboxylase, cadaverine is formed.
Why must TSI observations be made between 18 24 hours after incubation?
The anaerobic areas of the slant, such as the butt, will not revert to an alkaline state, and they will remain yellow. This happens with Salmonella and Shigella. TSI Agar medium should be read after an incubation of only 24 hours because a longer incubation time can cause a false negative.