Crystal Violet Lactose Agar

Specifications

Proteose peptone 5.00 G/L
Beef extract 3.00 G/L
Lactose 10.00 G/L
Crystal violet 0.0033 G/L
Agar 15.00 G/L
Final pH (at 25°C) 6.8 ñ 0.2

Directions :
Suspend 33 grams in 1000 ml purified / distilled water. Heat to boiling to dissolve the medium
completely. Sterilize by autoclaving at 15 lbs pressure (121°C) for 15 minutes. Cool to 45-50°C.
Mix well and pour into sterile Petri plates.
Principle :
Crystal violet lactose agar was recommended for the differentiation of pure cultures of pathogenic
from nonpathogenic strains of Staphylococci. Crystal violet is markedly inhibitory to Staphylococci.
A fair growth can be obtained at a 1:300,000 concentration of the dye when the medium is
inoculated heavily. So this medium is used for study of pure cultures where a mass inoculation can
be used rather than for primary isolation. Staphylococcal colonies show different colours when
cultured on Crystal violet Lactose Agar.