Sulfide
Sulfide is an inorganic anion of sulfur with the chemical formula S²⁻ or a compound containing one or more S²⁻ ions. Solutions of sulfide salts are corrosive. Sulfide also refers to chemical compounds large families of inorganic and organic compounds, e.g. lead sulfide and dimethyl sulfid…
What is the principle of TSI agar?
Feb 08, 2022 · What is the purpose of TSI agar in microbiology? It is used to determine the ability of an organism to ferment glucose, lactose, and sucrose, and their ability to produce hydrogen sulfide. It is used primarily to differentiate members of the Enterobacteriaceae family from other gram-negative rods.
What is tsi used for in microbiology?
Feb 24, 2020 · What is the purpose of TSI agar in microbiology? Triple sugar iron agar (TSI) is a differential medium that contains lactose, sucrose, a small amount of glucose (dextrose), ferrous sulfate, and the pH indicator phenol red. It is used to differentiate enterics based on the ability to reduce sulfur and ferment carbohydrates.
What is triple sugar iron agar used for?
Jul 16, 2013 · Addition of sucrose in TSI agar permits earlier detection of coliform bacteria that ferment sucrose more rapidly than lactose. Adding sucrose also aids the identification of certain gram-negative bacteria that could ferment sucrose but not lactose.
Why is the triple sugar iron (TSI) test important?
Jun 17, 2021 · Hardy Diagnostics Triple Sugar Iron (TSI) Agar is recommended for use in the differentiation of Enterobacteriaceae by their ability to ferment glucose, lactose, and sucrose, and their ability to produce hydrogen sulfide.
What is the purpose of using TSI Agar?
TSI Agar is used for the differentiation of gram-negative enteric bacilli based on carbohydrate fermentation and the production of hydrogen sulfide. TSI Agar is used for the determination of carbohydrate fermentation and hydrogen sulfide production in the identification of gram- negative bacilli.
What is the principle of TSI?
Principle of TSI test: The presence of fetrous sulphate and sodium thiosulphate fulfills the demand of sulphur and there is the indicator phenol red for the indication of change in the invironment of the media due to the production of acid or alkali.Apr 17, 2018
What is the purpose of TSI test and what are Enterobacteriaceae?
The test is used primarily to differentiate members of the Enterobacteriaceae family from other gram-negative rods. It is also used in the differentiation among Enterobacteriaceae on the basis of their sugar fermentation patterns.Jun 14, 2019
What is the purpose of the TSI test quizlet?
The TSI test is designed for the rapid separation and presumptive identification of enteric organisms. The Triple sugar-iron medium contains a lower concentration of glucose than of lactose and sucrose to allow for detection of the utlization of this substrate only.
What is the purpose of thiosulfate in the TSI Agar?
Sodium thiosulfate and ferrous sulfate are responsible for hydrogen sulfide production detection. Sodium thiosulfate acts as the substrate for enzymatic reduction and the resultant colorless hydrogen sulfide gas reacts with ferrous sulfate to produce ferrous sulfide, an insoluble black precipitate.
What is the composition of the TSI Agar?
TSI medium composition. Triple Sugar Iron Agar contains three carbohydrates: glucose (0.1%), sucrose (1%) and lactose (1%) + (beef extract, yeast, and peptones ...) + phenol red as an indicator of pH. During preparation, the tubes containing molten agar are tilted.
How is gas formation indicated in TSI Agar?
The formation of CO2 and hydrogen gas (H2) is indicated by the presence of bubbles or cracks in the agar or by the separation of the agar from the sides or bottom of the tube.Jan 4, 2022
What is the TSI for E coli?
Triple sugar iron agar (TSI) is a differential medium that contains lactose, sucrose, a small amount of glucose (dextrose), ferrous sulfate, and the pH indicator phenol red. It is used to differentiate enterics based on the ability to reduce sulfur and ferment carbohydrates.
Why is there more lactose and sucrose than glucose in TSI Agar?
Since lactose and sucrose are present in much higher concentrations than glucose, acid formation in the butt is due to these sugars, while the acid formation from glucose is suppressed by a rapid oxidation of the small amount of acid in the slanted area of the tube, resulting in a neutral or alcaline pH reaction when ...
Why is there more lactose and sucrose in TSI Agar than glucose quizlet?
Why is there more lactose and sucrose in TSI agar than glucose? 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.
For what bacteria would you use the TSI test quizlet?
-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 does triple sugar iron agar test for quizlet?
The TSI test is used to determine fermentation and sulfur reduction in Gram negative bacteria.
What is the Tsi test?
The Triple Sugar Iron (TSI) test is a microbiological test named for its ability to test a microorganism’s ability to ferment sugars and to produce hydrogen sulfide. An agar slant of a special medium with multiple sugars constituting a pH-sensitive dye (phenol red), 1% lactose, 1% sucrose, 0.1% glucose, as well as sodium thiosulfate ...
What is the purpose of the Enterobacteriaceae test?
Uses. The test is used primarily to differentiate members of the Enterobacteriaceae family from other gram-negative rods. It is also used in the differentiation among Enterobacteriaceae on the basis of their sugar fermentation patterns.
What is the color of the medium?
This is indicated by the change in colour of the medium from orange red to deep red. Sodium thiosulfate and ferrous ammonium sulfate present in the medium detects the production of hydrogen sulfide and is indicated by the black color in the butt of the tube.
Is hydrogen sulfide acidic?
However, hydrogen sulfide production requires an acid environment, thus the butt portion should be considered acid. TSI is not as sensitive in detecting hydrogen sulfide in comparison to other iron containing mediums, such as Sulfide Indole Motility (SIM) Medium.
Can bacteria ferment sugar?
Most bacteria have the ability to ferment carbohydrates, particularly sugars. Among them, each bacteria can ferment only some of the sugars, while it cannot ferment the others. Thus, the sugars, which a bacteria can ferment and the sugars, which it cannot is the characteristic of the bacteria and thus an important criterion for its identification.
What is Tsi agar?
The Triple Sugar Iron (TSI) agar is a culture medium named for its ability to test a microorganism’s ability to ferment sugars and to produce hydrogen sulfide.
Is hydrogen sulfide acidic?
However, hydrogen sulfide production requires an acid environment, thus the butt portion should be considered acid. TSI is not as sensitive in detecting hydrogen sulfide in comparison to other iron-containing mediums, such as Sulfide Indole Motility (SIM) Medium.
Can bacteria ferment sugar?
Most bacteria have the ability to ferment carbohydrates, particularly sugars. Among them, each bacterium can ferment only some of the sugars, while it cannot ferment the others. Thus, the sugars, which a bacterium can ferment and the sugars, which it cannot is the characteristic of the bacteria and thus an important criterion for its identification.
Objective
Principle
- The triple sugar- iron agar test employing Triple Sugar Iron Agar is designed to differentiate among organisms based on the differences in carbohydrate fermentation patterns and hydrogen sulfide production. Carbohydrate fermentation is indicated by the production of gas and a change in the colour of the pH indicator from red to yellow. To facilitate the observation of carbohydrat…
Method
- With a straight inoculation needle, touch the top of a well-isolated colony.
- Inoculate TSI by first stabbing through the center of the medium to the bottom of the tube and then streaking the surface of the agar slant.
- Leave the cap on loosely and incubate the tube at 35°-37°C in ambient air for 18 to 24 hours.
- Examine the reaction of medium.
Expected Results
- An alkaline/acid (red slant/yellow butt) reaction:It is indicative of dextrose fermentation only.
- An acid/acid (yellow slant/yellow butt) reaction:It indicates the fermentation of dextrose, lactose and/or sucrose.
- An alkaline/alkaline (red slant, red butt) reaction:Absence of carbohydrate fermentation results.
- An alkaline/acid (red slant/yellow butt) reaction:It is indicative of dextrose fermentation only.
- An acid/acid (yellow slant/yellow butt) reaction:It indicates the fermentation of dextrose, lactose and/or sucrose.
- An alkaline/alkaline (red slant, red butt) reaction:Absence of carbohydrate fermentation results.
- Blackening of the medium: Occurs in the presence of H2
Uses
- The test is used primarily to differentiate members of the Enterobacteriaceae family from other gram-negative rods.
- It is also used in the differentiation among Enterobacteriaceae on the basis of their sugar fermentation patterns.
Limitations
- It is recommended that biochemical, immunological, molecular, or mass spectrometry testing be performed on colonies from pure culture for complete identification.
- It is important to stab the butt of the medium. Failure to stab the butt invalidates this test. The integrity of the agar must be maintained when stabbing. Caps must be loosened during this test or...
- It is recommended that biochemical, immunological, molecular, or mass spectrometry testing be performed on colonies from pure culture for complete identification.
- It is important to stab the butt of the medium. Failure to stab the butt invalidates this test. The integrity of the agar must be maintained when stabbing. Caps must be loosened during this test or...
- TSI Agar must be read within the 18-24 hour stated incubation period. A false-positive reaction may be observed if read too early. A false-negative reaction may be observed if read later than 24 ho...
- An organism that produces hydrogen sulfide may mask acid production in the butt of the medium. However, hydrogen sulfide production requires an acid environment, thus the butt p…
References
- Tille P.M. 2014. Bailey and Scott’s diagnostic microbiology. Thirteen edition. Mosby, Inc., an affiliate of Elsevier Inc. 3251 Riverport Lane. St. Louis. Missouri 63043
- https://catalog.hardydiagnostics.com/cp_prod/Content/hugo/TripleSugarIronTSIAgar.htm
- , et al. Manual of Clinical Microbiology, American Society for Microbiology, Washington, D.C.
- https://vlab.amrita.edu/?sub=3&brch=76&sim=216&cnt=1
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