A rapid and simple method for distinguishing colonies of Proteus from those of Salmonella and Shigella

A rapid and simple method is described by which colonies of Proteus can be distinguished from those of Salmonella and Shigella and other non-lactose-fermenting organisms growing on MacConkey’s agar or desoxycholate citrate agar. The method is based on the ability of Proteus to produce urease constitutively. The enzyme was detected by the degradation of urea by the inoculum, thereby creating an alkaline reaction on pH-indicator paper.