CLED (Cystine Lactose-Electrolyte-Deficient) Agar 20. CLED Agar (Cystine-Lactose-Electrolyte-Deficient Agar) is a differential culture medium for use in isolating and enumerating bacteria in urine. It supports the growth of urinary pathogens and contaminants but prevents undue swarming of Proteusspecies due to its lack of electrolytes.