Description
Ornithine Decarboxylase Broth is a differential medium for identifying enteric Gram-negative bacilli through ornithine-decarboxylase activity.
Glucose fermentation first acidifies the broth and turns the indicator yellow. Organisms producing ornithine decarboxylase form alkaline putrescine and restore the medium to purple.
A fresh pure culture is inoculated, overlaid with sterile oil and incubated at 36 ± 1°C for up to 96 hours. Purple is positive and yellow is negative.
