HISTIDINE, LYSINE AND ORNITHINE DECARBOXYLASE BACTERIA IN SPANISH SALTED SEMIPRESERVED ANCHOVIES

We have studied the histidine decarboxylase activity in 118 strains of bacteria isolated from commercial samples of Spanish semi-preserved anchovies. The lysine and ornithine qualitative decarboxylase activity was also studied. The microorganism that presented the highest histamine activity was Morganella morganii, with 2123.26 +/- 414.00 ppm of histamine after 24 h of incubation at 37 degrees C. Two strains of Bacillus spp. and a strain of Staphylococcus xylosus were isolated with the capacity to form 10.54 and 110.00 ppm of histamine, respectively. However, the histidine decarboxylase activity of Bacillus spp. is not likely to be significant to human health, The microbic species with capacity to form histamine and those with capacity to form other biogenic amines were similar. Therefore, the prevention of the proliferation of microorganisms able to form histamine would also mean avoiding amine accumulation that leads to histamine food poisoning. The Niven medium was an efficient test to valutate the histamine production of isolated strains after an incubation of 24 h at 37 degrees C and using a backwards technique for quantification and detecting the false positives. This incubation time should be longer (48 h) when Bacillus is detected, with the finality to eliminate false negatives on the initial screening. The application of the enzymic technique for histamine quantification was excellent. In our research, we have observed that the number of microorganisms is an important factor in the accumulation of histamine, but other factors exist which also influence such accumulation, probably depending on the kind of enzyme decarboxylase.