EVALUATION OF HISTIDINE-DECARBOXYLASE ACTIVITY OF BACTERIA ISOLATED FROM SARDINE (SARDINA-PILCHARDUS) BY AN ENZYMATIC METHOD

A fast and simple enzymic method has been adapted to measure histidine decarboxylase activity in bacteria isolated from fish. It was possibl e to quantify the presence of histamine at levels higher than 1.03 x 1 0(-2) mu mol (3 ppm) per mi of culture medium. There was a good correl ation (r = 0.99) between the histamine content and the increase of abs orbance in the concentration range of 3 and 30 ppm. The method can be used for quantitation of the amount of histamine produced by a selecte d strain, and has the advantages of being low in cost, reliable, easy to use and fast to perform. Plesiomonas shigelloides, a bacterium freq uently isolated from fish and aquatic environments, has been identifie d as a new histamine-former in fish.