Triple sugar iron agar: Difference between revisions
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+ | *Contains three sugars (lactose, sucrose, and glucose) as well as iron, within a solid agar medium |
− | ** |
+ | **Peptone as a source of nitrogen |
− | ** |
+ | **Medium is originally reddish due to the phenol red indicator, which turns yellow in acidic conditions |
− | ** |
+ | **Tubes contain a well-oxygenated '''slant''' and a poorly-oxygenated '''butt''' which need to be interpreted separately |
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+ | **Inoculated with a stab down towards the butt followed by streaking the slant |
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+ | *After 18 to 24 hours at 35°C with a loose cap, the final colour depends on the metabolism of the four components |
− | ** |
+ | **Glucose alone fermented: butt turns yellow (acid), slant stays red (alkaline) (Alk/A) |
− | ** |
+ | **Lactose or sucrose fermented: both butt and slant turn yellow (acid) (A/A) |
+ | **No fermentation of glucose, lactose, or sucrose: both butt and slant stay red (Alk/Alk) |
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+ | **Iron: if hydrogen sulfide (H<sub>2</sub>S) is produced, the iron will turn black |
− | ** |
+ | **Gas may be formed with active fermentation of either glucose or lactose/sucrose |
− | == |
+ | ==Interpretation== |
+ | |||
+ | * Blackening suggests H<sub>2</sub>S production |
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{| class="wikitable" |
{| class="wikitable" |
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− | ! |
+ | !Slant!!Butt!!Gas!!H<sub>2</sub>S!!Fermentation!!Examples |
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+ | |Red||Red||No||No||—||[[Pseudomonas]] |
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+ | |Red||Yellow||No||No||G||[[Shigella]], [[Serratia]] |
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+ | |Yellow||Yellow||Yes||No||G/L/S |
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+ | |[[Escherichia species|Escherichia]], [[Klebsiella species|Klebsiella]], [[Enterobacter species|Enterobacter]] |
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+ | |Yellow||Yellow||Yes||Yes||G/L/S|| |
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+ | |Red||Yellow||Yes||Yes||G||[[Salmonella]], [[Proteus]] |
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− | == |
+ | ==Further Reading== |
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+ | *Microbe Online. [https://microbeonline.com/triple-sugar-iron-agar-tsi-principle-procedure-and-interpretation/ Triple Sugar Iron Agar (TSI): Principle, Procedure and Interpretation] |
[[Category:Diagnostics]] |
[[Category:Diagnostics]] |
Latest revision as of 10:29, 8 October 2020
- Contains three sugars (lactose, sucrose, and glucose) as well as iron, within a solid agar medium
- Peptone as a source of nitrogen
- Medium is originally reddish due to the phenol red indicator, which turns yellow in acidic conditions
- Tubes contain a well-oxygenated slant and a poorly-oxygenated butt which need to be interpreted separately
- Inoculated with a stab down towards the butt followed by streaking the slant
- After 18 to 24 hours at 35°C with a loose cap, the final colour depends on the metabolism of the four components
- Glucose alone fermented: butt turns yellow (acid), slant stays red (alkaline) (Alk/A)
- Lactose or sucrose fermented: both butt and slant turn yellow (acid) (A/A)
- No fermentation of glucose, lactose, or sucrose: both butt and slant stay red (Alk/Alk)
- Iron: if hydrogen sulfide (H2S) is produced, the iron will turn black
- Gas may be formed with active fermentation of either glucose or lactose/sucrose
Interpretation
- Blackening suggests H2S production
Slant | Butt | Gas | H2S | Fermentation | Examples |
---|---|---|---|---|---|
Red | Red | No | No | — | Pseudomonas |
Red | Yellow | No | No | G | Shigella, Serratia |
Yellow | Yellow | Yes | No | G/L/S | Escherichia, Klebsiella, Enterobacter |
Yellow | Yellow | Yes | Yes | G/L/S | |
Red | Yellow | Yes | Yes | G | Salmonella, Proteus |