o-Nitrophenyl-beta-D-galactopyranoside-urease-indole broth, a new composite tube medium for Salmonella screening.

A new composite broth medium combining o-nitrophenyl-beta-D-galactopyranoside (ONPG) and urease and indole tests in a single tube is described. High-level agreement with individual conventional tests was recorded in comparative studies with 2,412 cultures of members of the family Enterobacteriaceae, i.e., 100% agreement with the exception of Hafnia spp. (96.3% agreement) for the ONPG test and Citrobacter, Enterobacter, and Hafnia spp. (75, 86.4, and 98.2% agreement, respectively) for the urease test. The new medium seems especially promising as a screen for Salmonella subgroup I which encompasses most pathogenic Salmonella species other than the Arizona subgroup.