TSI

From Wikipedia, the free encyclopedia

TSI may refer to:

• TSI, an independent nightclub, venue, and art gallery in Jacksonville, FL
• The Spaghetti Incident?, a covers album by Guns N' Roses.
• Thyroid Stimulating Immunoglobulin
• Televisione svizzera di lingua italiana
• Torres Strait Islanders, an Australian indigenous people
• Torres Strait Islands
• Time-Slot Interchange, a technique used to switch networks
• Trading Standards Institute, a British professional association
• TeleSensory, Inc., a maker of speech products and products intended for the blind
• Town Sports International, an operator of fitness facilities

TSI test is a determinitive test used when dealing with Gram neg. Rods. TSI stands for triple sugar iron, and is in the form of a test tube, with a slant agar. The three sugars used in a TSI test are lactose, glucose and sucrose. The concentrations of these sugars are; lactose 1%, Sucrose 1%, Glucose .1%. The concentration difference is what enables you to differentiate between which saccharide is being digested. Phenyl red is the indicator used in determining carbohydrate fermentation. When a bacteria breaks down the carbohydrate and acid by product is produced, resulting in an increased acidity of the solution. Phenyl red when in a ph of 7 or higher is red, pink at 8 or higher. However when the ph drops below 6.8 phenyl red turns yellow. The TSI tube is read by first looking at the slant to see if lactose was fermented, yellow indicating it was, then second by looking at the butt of the test tube to see if glucose was fermented, once again yellow indicates positive fermentation. Secondary tests involved in the TSI include the formation of gas, little bubbles in the agar, or Hydrogen Sulfide H2S, which is indicated by a black precipitate at the bottom of the tube. As a rule of thumb, if H2S is produced one can always deduce that glucose fermentation has occurred as well, since the black bottom might inhibit you from determining if Glucose was fermented (yellow bottom).