CLED/MacConkey Agar or CLED/MacConkey III Agar
Overview
CLED Agar: In 1960, Sandys reported on the development of a new method of preventing the swarming of Proteus on solid media by restricting the electrolytes in the culture medium. Previous chemical methods used to inhibit swarming by Proteus included the addition of chloral hydrate, alcohol, sodium azide, surface-active agents, boric acid, and sulfonamides to the culture medium. This electrolyte-deficient medium of Sandys was modified by Mackey and Sandysfor use in urine culture by substituting lactose and sucrose for the mannitol and increasing the concentrations of the bromothymol blue indicator and of the agar. These two investigators further modified the medium by the incorporation of cystine to enhance the growth of cystine-dependent “dwarf colony” coliforms and by deletion of sucrose. They designated the new medium as Cystine-Lactose-Electrolyte-Deficient (CLED) medium and reported it to be ideal for dip-inoculum techniques and for urinary bacteriology in general. MacConkey Agar: MacConkey Agar is based on the bile salt-neutral red-lactose agar of MacConkey. The original MacConkey medium was used to differentiate strains of Salmonella typhosa from members of the coliform group. Formula modifications improved the growth of Shigella and Salmonella strains. These modifications included the addition of 0.5% sodium chloride, decreased agar content, and altered bile salts and neutral red concentrations. The formula improvements gave improved differential reactions between these enteric pathogens and the coliform group. MacConkey Agar contains crystal violet and bile salts that inhibit gram-positive organisms and allow gram negative organisms to grow. Isolated colonies of coliform bacteria are brick red in color and may be surrounded by a zone of precipitated bile. This bile precipitate is due to a local pH drop around the colony due to lactose fermentation. Colonies that do not ferment lactose (such as typhoid, paratyphoid and dysentery bacilli) remain colorless. When lactose nonfermenters grow in proximity to coliform colonies, the surrounding medium appears as cleared areas. MacConkey Agar is listed as one of the recommended media for the isolation of E. coli from nonsterile pharmaceutical products. MacConkey Agar Base is prepared without added carbohydrates, which permits their addition either individually or in combination. It is recommended that carbohydrates such as sucrose or lactose be added in a concentration of 1% to the basal medium.
Intended Use
CLED Agar and MacConkey Agar (Biplate) medium are used for urinary microbiology analysis. CLED Agar is a medium for isolating, enumerating, and presumptively identifying microorganisms from urine. MacConkey agar is a selective and differential medium used to detect and isolate gram-negative organisms.
Product Information
Category
Catalog Number
SP90C1011, SP90C1012
Pack Size
10 per pack