A sensitive method for demonstration of decarboxylase activities amongst Enterobacteriaceae without use of pH indicators.

Lysine decarboxylase and ornithine decarboxylase activities have been demonstrated in a range of Enterobacteriaceae and related taxa by methods not involving pH indicators. Detection of the diamines produced, cadaverine and putrescine, was achieved by use of reagents based on 5-nitrosalicylaldehyde in the presence of triethanolamine and nickel ions. The method has been shown to be a simple and sensitive means for demonstration of decarboxylase activities when organisms were grown in the presence of the appropriate amino acid. Formation of highly coloured insoluble metal chelates was indicative of enzymatic activity. Results correlated well with existing indicator methods while being superior to the latter with respect to interpretation.