Use of urea filter paper disc to detect urease activity in Enterobacteriaceae by multipoint replication techniques

A new method of detecting urease activity in Enterobacteriaceae was developed. An 8.5 cm filter paper disc impregnated with 20% urea and 0.5% bromocresol purple was placed on the surface of a glucose fermentation plate after inoculation with a multipoint replicator and overnight incubation. This method was compared with the commercially prepared Mast urea agar (Multipoint) and Fuscoe's Urea Plate Medium. A total of 240 routine isolates of Enterobacteriaceae were tested for urease activity using the three methods. Sixty five isolates were positive by the three methods while 33 isolates gave differing results. The urea disc method was more sensitive for detecting urease activity in isolates of Klebsiella species, Morganella morganii, and Yersinia enterocolitica. It also overcame the problem associated with the other two media of diffusion of alkali end products through the medium.