title: Rapid ornithine decarboxylase test for the identification of enterobacteriaceae.
abstract: Conventional methods for detecting ornithine decarboxylase activity require an extended period of incubation. However, with a few simple modifications, accurate results were obtained within a few hours rather than several days. The broth medium was modified, primarily by omitting glucose and by decreasing the pH to 5.5. A 1-ml amount of this broth was inoculated with one colony and then overlaid with sterile mineral oil. Within 2 to 4 hr, the pH increased if ornithine was decarboxylated, thus changing the color of the internal pH indicator to a dark purple. If the amino acid was not decarboxylated, the pH decreased to pH 5.0 to 5.2, enough to give a definite yellow color. With 347 selected clinical isolates, the rapid test gave results identical to those obtained in 1 to 4 days with Moeller's decarboxylase medium. Less reliable results were obtained with Difco's decarboxylase medium with 0.3% agar which was stabinoculated and read after 18 to 24 hr without a mineral oil seal. The rapid ornithine decarboxylase test represents a simple, accurate technique which is well suited for the clinical microbiology laboratory.
mesh_terms: D001431:Bacteriological Techniques; D002262:Carboxy-Lyases / Q000378:metabolism*; D003470:Culture Media; D003653:Decarboxylation; D004755:Enterobacteriaceae / Q000145:classification* / Q000201:enzymology; D005069:Evaluation Studies as Topic; D006863:Hydrogen-Ion Concentration; D008722:Methods; D008899:Mineral Oil; D009952:Ornithine; D013997:Time Factors
chemical_list: D003470:Culture Media; D008899:Mineral Oil; D009952:Ornithine; D002262:Carboxy-Lyases