Selective Media for the Isolation, Cultivation and Differentiation ofBacillus coliandB. lactis aerogenes

Abstract

1. An agar medium is described which enables a direct estimation of the numbers of coliform bacilli in a water or milk sample to be made.2. An enrichment medium for B. lactis aerogenes is one containing in every 100 c.c. of peptone water 0·5 g. sodium citrate, 0·25 g. soluble starch and 1 c.c. of a 1 per cent, watery solution of neutral red.3. Enrichment media for B. coli are: (a) lactose peptone water containing in every 100 c.c., 1 g. sodium sulphite anhydrous and 2 c.c. of 1 per cent, rosolic acid in absolute alcohol; (b) lactose peptone water containing in every 100 c.c., 2 c.c. of a 40 per cent, solution of hexamine in water.4. Importance is attached to the capacity to ferment starch possessed by B. lactis aerogenes.5. The application of these media to the examination of water and milk is indicated.