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 frozen albacore stored either at -18 or -25 degrees C and investigated for their abilities to produce biogenic amines. As a preliminary screening, all 227 strains were tested in either Niven or Niven modified medium, which allowed the selection of 25 presumptive histamine-producing strains. High-pressure liquid chromatography revealed that only 10 of the 25 strains selected were able to produce low histamine concentrations (<25 ppm) in tryptic soy broth medium supplemented with 2% histidine. None of the 25 strains tested produced putrescine or spermine, whereas 6 strains produced spermidine. Histamine production by Stenotrophomonas maltophilia strain 25MC(6) was not prevented 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 determined 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 incubation at 37 degrees C. S. maltophilia strain 15MF, initially obtained from fresh albacore tuna, produced up to 2,399 ppm and 4,820 ppm of cadaverine after 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 strains of the species S. maltophilia, previously known as Pseudomonas and Xanthomonas maltophilia, isolated from fresh and frozen albacore tuna.