CLED agar (Cysteine Lactose Electrolyte Deficient medium) is a valuable non-inhibitory growth medium used in the isolation and differentiation of urinary organisms. Being electrolyte deficient, it prevents the swarming of Proteus species. Lactose fermenters produce yellow colonies on CLED agar; non-lactose fermenters appear blue. It has a pH of approximately 7.3. CLED agar contains: