Scientific Publications by FDA Staff

Appl Environ Microbiol 2016 Apr;82(7):2167-76

Photobacterium angustum and Photobacterium kishitanii: psychrotrophic high histamine-producing bacteria indigenous to tuna.

Bjornsdottir-Butler K, McCarthy S, Dunlap PV, Benner RA Jr

Scombrotoxin fish poisoning (SFP) remains the main contributor to fish poisoning incidents in the United States despite efforts for its control. Psychrotrophic histamine-producing bacteria (HPB) indigenous to scombrotoxin-forming fish may contribute to the incidence of SFP. We examined gills, skin, and anal vent of yellowfin (n=3), skipjack (n=1), and albacore tuna (n=6) for the presence of indigenous HPB. Thirteen HPB were isolated from the anal vent samples from albacore (n=3) and yellowfin tuna (n=2). Four of these isolates were identified as Photobacterium kishitanii and nine as Photobacterium angustum, these isolates produced 560-603 and 1582-2338 ppm histamine in marine broth containing 1% histidine (25 degrees C, 48h), respectively. Optimum growth temperatures and salt concentrations were 26-27 degrees C and 1% salt for P. kishitanii and 30-32 degrees C and 2% salt for P. angustum in LSW-70. The optimum activity of the HDC enzyme was at 15-30 degrees C for both species. At 5 degrees C, P. kishitanii and P. angustum had growth rates of 0.1 and 0.2 h-1 and the activity of histidine decarboxylase (HDC) enzymes was 71% and 63%, respectively. These results show that indigenous HPB in tuna are capable of growing at elevated and refrigeration temperatures. These findings demonstrate the need to examine the relationships between the rate of histamine production at refrigeration temperatures, seafood shelf life, and regulatory limits.