Bile Esculin Agar Base

Specifications

Ingredients : gms/lit.
Peptone 5.00
Meat extract B # 3.00
Bile 40.00
Ferric citrate 0.50
Agar 15.00
# Equivalent to Beef extract
Final pH (at 25°C) : 6.6 + 0.2
Directions :
Suspend 31.75 grams in 500 ml distilled water. Heat to boiling to dissolve the medium completely. Cool to
45-50°C.Add rehydrated contents of 1 vial of Esculin Mix and dispense into tubes or flasks as
desired. Sterilize by autoclaving at 15lbs pressure (121°C) for 15 minutes. Allow the tubed medium to
solidify in slanted position.
Principle :
Peptone and meat extract B serve as sources of carbon, nitrogen, amino acids, vitamins and essential
growth nutrients. Bile inhibits most of the other accompanying bacteria. Esculin when added as a
supplement in the medium is hydrolyzed to esculetin and dextrose. Esculetin reacts with ferric citrate to
form a dark brown or black complex, visualized as a zone of black precipitate around the colonies. If the
media is dispensed in tubes in the form of slants, a positive reaction is indicated by blackening of more
than half of the slant within 24-48 hours. If blackening is totally absent or if less than half of the slant is
blackened within 24-48 hours, the test is negative.