CLED Agar With Bromo Thymol Blue

PRODUCT SUMMARY AND EXPLANATION: CLED Agar (Cystine Lactose- Electrolyte- Deficient Agar) w/ Bromo Thymol Blue is a differential medium that was described by Mackey and Sandys to isolate coliforms from urine samples. On a solid medium, Sandys reported that the swarming of Proteus species can be controlled by restricting the electrolytes. Later on, Sandys medium was modified by Mackey and Sandys, by replacing mannitol with lactose and sucrose and elevating the concentration of agar and bromothymol blue. This formulation was further modified by the same authors, called C.L.E.D. (Cystine-Lactose-Electrolyte-Deficient) by deleting the sucrose and by including L-cystine for promoting the growth of cystine dependant dwarf colony coliforms.

PRINCIPLE: Casein enzymatic hydrolysate and Peptic digest of animal tissue act as a source of amino acids and nitrogen. The beef extract is a source of minerals and vitamins. Sodium chloride has been omitted by substituting lactose and increasing the amount of indicator and agar which inhibits the Proteus swarming and supports the growth of a great majority of bacteria causing urinary tract infections and is used to differentiate and identify them. Lactose is a fermentable sugar that is fermented by lactose fermenters and acidic end products are released in the medium due to which the medium pH is shifted towards acidity. Omitting of sucrose and adding L – cystine added as a growth supplement for cystine-dependent coliforms. The acid in the medium is detected by the indicator dye Bromothymol blue, changing the medium color from green to yellow. Agar acts as a solidifying agent. As the electrolytes present in the medium are reduced, it suppresses the Proteus swarming, allowing the vast majority of other coliforms to grow in the medium. Spread plate technique or a dip slide for detection of bacteria in urine is the best technique for CLED Agar.