TSI (Triple Sugar Iron) Test 32 Questions with Verified Answers
List the tests that are involved with TSI. - CORRECT ANSWER H2S Gas and Carbohydrate
... [Show More] Fermentation
What is the media for H2S Gas? - CORRECT ANSWER TSI agar
What method do you use to place content on the media? - CORRECT ANSWER stab and drag motion
what is the substrate for H2S gas? - CORRECT ANSWER cystein
What is the product for H2S gas? - CORRECT ANSWER H2S
What is the reagent for H2S gas? - CORRECT ANSWER iron in media
What is the pH indicator for H2S gas? - CORRECT ANSWER none
What is the + appearance of H2S gas? - CORRECT ANSWER Black ppt. when H2S reacts with iron to form iron sulfied
What is the positive organisms for H2S gas? - CORRECT ANSWER S. typhimurium and P. vulgaris
What is the media for Carbohydrate fermentation? - CORRECT ANSWER TSI agar
what is the substrate for the carbohydrate fermentation? - CORRECT ANSWER glucose, sucrose, and lactose
whats it the product of carbohydrate fermentation? - CORRECT ANSWER organic acids
what is the reagent for carbohydrate fermentation? - CORRECT ANSWER none
What is the pH indicator for carbohydrate fermentation? - CORRECT ANSWER phenol red in agar
What is the + appearance of carbohydrate fermentaiton? - CORRECT ANSWER media is yellow (acidic) or red (alkaline)
How should you record the reaction of carbohydrate fermentaiton - CORRECT ANSWER slant or butt
What does K/A mean? - CORRECT ANSWER glucose only
What does A/A mean? - CORRECT ANSWER sucrose & lactose (+/- glucose)
What does K/K mean? - CORRECT ANSWER none fermented
What does a black "butt" mean? - CORRECT ANSWER acidic
What is the TSI test used for? What are the two ways bacteria are inoculated - CORRECT ANSWER used to distinguish between enteric bacteria
List the ingredients in the agar and explain their relevance to the test. - CORRECT ANSWER Peptone: source of amino acids, including cysteine
Phenol red: pH indicator
Glucose: carbon source
Sucrose: carbon source
Lactose: carbon source
FeSO4 (ferrous sulfate): reacts with H2S gas to form ferrous sulfide (FeS)
Explain why there is a lower concentration of glucose in the agar than lactose and sucrose. - CORRECT ANSWER because the glucose gets used up first since it is a cell's main source of energy
H2S is produced from the breakdown of which sulfur-containing amino acid? - CORRECT ANSWER cysteine
If the bacteria cannot ferment any of the sugars, what happens? - CORRECT ANSWER no acid is produced so pH not reduced
-aerobic respiration of peptone in the slant produces alkaline products
**no fermentation of sugars-pink slant/red butt
If the bacteria can only ferment glucose, what happens? - CORRECT ANSWER acid produced by fermentation will turn the agar yellow at first
-glucose runs out->catabolize peptone aerobically in slant
**only glucose fermented -pink slant/yellow butt (butt stays yellow)
If the bacteria can ferment glucose and lactose or sucrose, what happens? - CORRECT ANSWER glucose used up first
-bacteria will synthesize certain enzymes to use other sugars for energy
-fermenting lactose or sucrose produces acid
-whole slant turns yellow
**yellow slant/yellow butt
If the bacteria can metabolize cysteine, what happens? - CORRECT ANSWER cysteine contains sulfer so surfer is released as H2S if cysteine is metabolized
-agar contains FeSO4 which reacts with H2S to form ferrous sulfide (FeS)
**black precipitate in butt
How can you tell that acid is produced in the bottom of the tube if its black? How would you record a black bottom? - CORRECT ANSWER assume there is acid bc H2S formation requires acidic conditions
-Y+
What do TSI results mean about bacterial metabolism? - CORRECT ANSWER Can tell us:
-obligate aerobe vs. facultative (which enteric are supposed to be)
-ability to ferment glucose only or lactose/sucrose as well
-if fermentation produces gas or not
-if the bacteria are able to metabolize cysteine, producing H2S gas
How do you record TSI results? - CORRECT ANSWER Write slant color 1st: R for red/pink or Y for yellow (R=no acid so not enteric bacteria bc obligate aerobe, Y=acid)
Write b u t t color 2nd (R, Y, Y+)
3rd: gas (yes/no) G
FOR EXAM BE ABLE TO INTERPRET DRAWING/PICTURE OF TSI TUBE AND GIVE CODE (EX. R/R), WHAT SUGARS ARE USED, IS GAS PRESENT, IS CYSTEINE BROKEN DOWN :) - CORRECT ANSWER [Show Less]