A New Selective Isolation Medium for the Vibrio Group

Abstract

It was reported by Nakanishi (1963) that a new selective plating medium consisting of ox bile, -thiosulphate, citrate, lactose, sucrose and skim milk is suitable for the selective isolation of both cholera vibrio and pathogenic halophilic bacteria (Vibrio parahaemolyticus).This composition was modified by the authors as follows and named TCBS agar medium peptone 10 g/l, yeast extract 5 g/l, Na. citrate 10 g/l, Na. thiosulphate 10 g/l, NaCl 10 g/l, Fe. citrate 1 g/l, ox bile (powder) 5 g/l, Na. cholate 3 g/l, sucrose 10 g/l, agar 15 g/l, B. T. B (0.2 % aqueous sol.) 20 ml/l, thymol blue (0.2 % aqueous sol.) 20 ml/l ; pH 8.6.After 24 hours incubation on this medium, freshly isolated strains of cholera vibrio and sucrose fermenting strains ofVibrio parahaemolyticusproduce large, smooth and yellow-coloured colonies, and sucrose-non-fermenting strains blue colonies.Gram positive bacteria, proteus and coli-group are strongly inhibited. Some strains of proteus can grow on this medium, but the colonies are so small and colorless that they are easily distinguishable.