Triple Sugar Iron Test Exam 38 Questions with Verified Answers
For what bacteria would you use the TSI test? - CORRECT ANSWER Gram negative bacilli
... [Show More] such as enterobacteriaceae.
How would you identify an acidic slant? - CORRECT ANSWER If the slant goes from red to yellow on the phenol red.
Why is there more lactose and sucrose in TSI agar than glucose? - CORRECT ANSWER In order to distinguish bacteria that can only ferment glucose from bacteria that ferment lactose and sucrose. It will also allow for greater acid production.
TEST RESULTS: red slant/red butt - CORRECT ANSWER INTERPRETATION: no fermentation (NC)
TEST RESULTS: red slant/yellow butt - CORRECT ANSWER INTERPRETATION: glucose fermentation (A)
TEST RESULTS: yellow slant/yellow butt - CORRECT ANSWER INTERPRETATION: lactose and/or sucrose fermentation (A/A)
TEST RESULTS: cracks or lifting in agar - CORRECT ANSWER INTERPRETATION: gas production (G)
TEST RESULT: blackening o agar - CORRECT ANSWER INTERPRETATION: hydrogen sulfide production (H2S+)
What is use to test TSI? - CORRECT ANSWER an agar slant that contains lactose and sucrose each in a 1% concentration and glucose in a 0.1% concentration.
What is also included to detect acid produce during fermentation? - CORRECT ANSWER pH indicator, phenol red
What happens if only glucose is fermented by the bacterium tested? - CORRECT ANSWER only a small amount of acid will be produced, turning just the butt of the slant yellow.
What happens if either lactose or sucrose are fermented? - CORRECT ANSWER their greater concentration will allow greater acid production resulting in the entire butt and slant turning yellow.
What should be use to distinguish bacteria? - CORRECT ANSWER the amount of acid that only ferment glucose from bacteria that ferment lactose and/or sucrose.
glucose - CORRECT ANSWER enterobacteriaceae
lactose and/or sucorse - CORRECT ANSWER other intestinal bacilli
What is use to inoculated the TSI slants? - CORRECT ANSWER needle
What does the surface of the slant have to be done once removed from the butt? - CORRECT ANSWER the surface of the slant should be streaked by dragging the needle lightly across the slanted surface of the agar in a siz-zag motion.
How long should the TSI slant be incubated for? - CORRECT ANSWER 24-48 hours
Fermentation of glucose - CORRECT ANSWER the slant remains red because of the limited glucose substrate and thus, limited acid production.
Fermentation of lactose and/or sucrose - CORRECT ANSWER the excessive concentration of these sugars leads to excessive acid production turning the entire slant and butt yellow.
Gas formation - CORRECT ANSWER splitting or cracks in the agar or lifting of the agar from the bottom of the tube.
Hydrogen sulfide production - CORRECT ANSWER blackening of the agar.
Red butt and red slant indicat - CORRECT ANSWER none of the sugars were fermented, and neither gas nor hydrogen sulfide were produced.
what is the purpose of the triple sugar iron test? - CORRECT ANSWER -the TSI test is designed to differentiate among the different groups or genera of the Enterobacteriaceae, which are all gram-negative bacilli capable of fermenting glucose with the production of acid, and to distinguish the Enterobacteriacase from other gram-negative intestinal bacilli.
What is the enterobacteriacase? - CORRECT ANSWER -all gram negative bacilli capable of fermenting glucose with the production of acid.
what is the differentiation based on? - CORRECT ANSWER The differentiation is made on the basis of the differences in carbohydrate fermentation patterns and hydrogen sulfide production.
what kind of tool does this test use? - CORRECT ANSWER -agar slant (contains lactose and sucrose (1%) & glucose (0.1%))
-pH indicator (phenol red) used to detect acid produced during fermentation
what happens if only glucose is fermented? - CORRECT ANSWER -if only glucose is fermented by the bacterium tested, only a small amount of acid will be produced, turning just the butt (bottom) of the slant yellow.
-this is because there is only a little amount of glucose available (0.1% vs 1%)
what happens if either lactose or sucrose are fermented? - CORRECT ANSWER -if either lactose or sucrose are fermented, their greater concentration will allow greater acid production resulting in the ENTIRE butt and slant turning yellow.
Thus, we can use the amount of acid produced to distinguish bacteria that ONLY ferment glucose (Enterobacteriaceae) from bacteria that ferment lactose and/or sucrose (other intestinal bacilli)
how are TSI inoculated? - CORRECT ANSWER -using inoculating needle
-first, the butt of the slant is stabbed by pushing the needle into the agar to within 0.5 cm of the bottom of the tube.
-then, as the needle is removed from the butt, the surface of the slant is streaked by dragging the needle lightly across the slanted surface of the agar in a zig-zag motion.
After inoculating the TSI slants for 24-48 hours, what are the reactions? - CORRECT ANSWER -yellow butt and red slant = fermentation of ONLY glucose. The slant remains red because of the limited glucose substrate and thus, limited acid production.
-yellow butt and yellow slant = fermentation of lactose and/or sucrose. the excessive concentration of these sugars lead to ecvessive acid production turning the entire slant and butt yellow.
-gas formation indicated by splitting or cracks in the agar or lifting of the agar from the bottom of the tube.
-hydrogen sulfide production indicated by blackening of the agar.
-red butt and red slant indicating that none of the sugars were fermented, and neither gas nor hydrogen sulfide were produced. j
what bacteria would you use the TSI test for? - CORRECT ANSWER -enterobacteriaceae
how would you identify an acidic slant? - CORRECT ANSWER -the slant turns yellow if acidic.
why is there more lactose and sucrose in TSI agar than glucose? - CORRECT ANSWER -we can use the acid produced to distinguish bacteria that ONLY ferment glucose (enterobacteriaceae) from bacteria that ferment lactose and/or sucrose (other intestinal bacilli)
red slant/red butt - CORRECT ANSWER no fermentation
red slant/yellow butt - CORRECT ANSWER glucose fermentation
yellow slant/yellow butt - CORRECT ANSWER lactose and/or sucrose fermentation
cracks or lifting in agar - CORRECT ANSWER gas production
blackening of agar - CORRECT ANSWER hydrogen sulfide production [Show Less]