Histamine and cadaverine production by bacteria isolated from fresh and frozen albacore (Thunnus alalunga)

Two hundred twenty-seven bacterial strains were isolated from fresh and fro zen albacore stored either at -18 or -25 degrees C and investigated for the ir abilities to produce biogenic amines. As a preliminary screening, all 22 7 strains were tested in either Niven or Niven modified medium, which allow ed the selection of 25 presumptive histamine-producing strains. High-pressu re liquid chromatography revealed that only 10 of the 25 strains selected w ere able to produce low histamine concentrations (<25 ppm) in tryptic soy b roth medium supplemented with 2% histidine. None of the 25 strains tested p roduced putrescine or spermine, whereas 6 strains produced spermidine. Hist amine production by Stenotrophomonas maltophilia strain 25MC(6) was not pre vented at 4 degrees C, and the levels of this amine reached concentrations of 25.8 ppm after 6 days. Three S. maltophilia strains showed strong lysine -decarboxylating activity. Their cadaverine formation capacity was determin ed by high-pressure liquid chromatography in tryptic soy broth supplemented with 1% lysine; this revealed that the three S. maltophilia strains tested produced more than 700 ppm of cadaverine during the first 24 h of incubati on at 37 degrees C. S. maltophilia strain 15MF, initially obtained from fre sh albacore tuna, produced up to 2,399 ppm and 4,820 ppm of cadaverine afte r 24 and 48 h of incubation at 37 degrees C, respectively. To our knowledge , this is the first report on histamine and cadaverine production by strain s of the species S. maltophilia, previously known as Pseudomonas and Xantho monas maltophilia, isolated from fresh and frozen albacore tuna.