In nine laboratories 1% lactose ricinoleate broth has been investigated as a possible alternative to brilliant green bile broth as a confirmatory medium for coliform organisms and Escherichia coli.

Although the results varied considerably from one laboratory to another, in the sum of the results and in the majority of the participating laboratories 1% lactose ricinoleate produced fewer false negative reactions than brilliant green bile broth as a confirmatory medium at both 37 and 44° C.

Although both media are satisfactory, 1% lactose ricinoleate broth can be recommended as an alternative to brilliant green bile broth for the confirmation of coliform organisms and Esch. coli from presumptive positive tubes in the examination of water samples, as it is not subject to the known variability of brilliant green and ox-bile.