Biomed MDx
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 Sandys for 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 ideal for dip-inoculum techniques and urinary bacteriology in general.
