Rippey-Cabelli Agar Base

Rippey-Cabelli Agar Base is recommended for differential and selective isolation of Aeromonas hydrophila from water samples using membrane filter technique. This medium formulated by Rippey and Cabelli is a differential medium as it depends on the ability of organisms to ferment trehalose and selective due to the incorporation of selective agents. Ampicillin, sodium deoxycholate and ethanol are the selective agents inhibiting gram-positive bacteria, coliforms, Shigella species, Proteus mirabilis and Actinomyces. Ethanol inhibits overgrowth of Klebsiella species on the filter. Most of the Enterobacteriaceae ferment trehalose, therefore it is difficult to distinguish Aeromonas from Enterobacteriaceae. The medium gives higher specificity and sensitivity when pure cultures are used. Membrane filters through which water samples have been filtered are aseptically placed on Rippey-Cabelli Agar Base plates and incubated at 35-37°C for 24 hours. Aeromonas ferments trehalose and forms yellow colonies.