Microbiology lab 4 Flashcards
What is the TSI test?
The tripe sugar Iron agar. It is a differential medium employed in identifying gram negative bacilli. Tests for fermentation if glucose, lactose, and/or sucrose; production of hydrogen sulfide; and gas production (CO2)
What are the possible results of the TSI test?
1) A/A: (yellow/hello) ferments lactose and/or sucrose, in addition to glucose
2) K/A: (red/yellow) alkaline slant, acid butt-ferments glucose only
3) K/K: (red/red)- none of the sugars are fermented
CO2 formation causes a crack/airpocket in agar
What is the MIO test?
Motility-Indole-Ornithine Decarboxylase test. Tests for motility of bacteria. Tests for indole production which is a byproduct of tryptophan breakdown. Tests for ornithine decarboxylase by testing ability to decarboxylate ornithine to the diamine putrescine.
What are the interpretation results of the MIO test?
- Motility: Positive will have organisms migrate from stab line (cloud)/Negative will have growth along stab line only
- ODC: Positive will have turbid purple to faded out purple-gray at the bottom 2/3 of the tube/ Negative will have bright, clear yellow at the bottom of the tube
- Indole (perform last): Positive will have red color/Negative will have no red develops and will remain the color of kovacs’ reagent (yellow)
Citrate Utilization test
Determines ability of organism to use sodium citrate as sole source of carbon. i.e. enterobacter aerogenes and citrobacter spp
What are the interpretation results of the citrate test?
Positive: Grown on slant, alkaline reaction (blue)/ Negative: No color change (green)
What is the urease test?
Test to check an organisms ability hydrolyze urea to ammonia, CO2 and H2O by enzyme urease
How is the urease test interpretted?
Positive: Hot pink on slant or extending into the entire butt. Negative: No change, agar remains peach or turns yellow
