Triple sugar iron agar: Difference between revisions

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

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

@@ Line 12: / Line 12: @@
 ==Interpretation==
+* Blackening suggests H<sub>2</sub>S production
 {| class="wikitable"
-!Slant!!Butt!!Gas!!H2S!!Fermentation!!Examples
+!Slant!!Butt!!Gas!!H<sub>2</sub>S!!Fermentation!!Examples
 |-
-|Red||Red||No||No||—||''Pseudomonas''
+|Red||Red||No||No||—||[[Pseudomonas]]
 |-
-|Red||Yellow||No||No||G||''Shigella'', ''Serratia''
+|Red||Yellow||No||No||G||[[Shigella]], [[Serratia]]
 |-
 |Yellow||Yellow||Yes||No||G/L/S
-|[[Escherichia species|''Escherichia'']], [[Klebsiella species|''Klebsiella'']], [[Enterobacter species|''Enterobacter'']]
+|[[Escherichia species|Escherichia]], [[Klebsiella species|Klebsiella]], [[Enterobacter species|Enterobacter]]
 |-
 |Yellow||Yellow||Yes||Yes||G/L/S||
 |-
-|Red||Yellow||Yes||Yes||G||''Salmonella'', ''Proteus''
+|Red||Yellow||Yes||Yes||G||[[Salmonella]], [[Proteus]]
 |}