TYPE-E BOTULISM ASSOCIATED WITH VACUUM-PACKAGED HOT-SMOKED WHITEFISH

On January 16, 1997 two Germans got botulism after eating hot-smoked C anadian whitefish produced in Finland. The serum sample of one of the patients contained 6 MLD/ml of botulinum toxin. The type of toxin was identified as E by the toxin neutralization test and the botulinum neu rotoxin type E (BoNT/E) gene was also amplified from the serum by poly merase chain reaction (PCR), but C. botulinum could not be isolated fr om the positive serum sample. The remains of the hot-smoked whitefish eaten by the patients contained botulinum toxin detected by the mouse bioassay and the BoNT/E gene as determined by PCR. C. botulinum was is olated from the fish sample and it was confirmed to be type E by the m ouse bioassay and by PCR. Eleven other fish samples from the same lot did not contain botulinum toxin nor any BoNT gene. The incriminated fo od was processed on the 9th and 10th of January, 1997 from frozen whit efish imported to Finland from Canada. The pulsed-field gel electropho retic pattern of the isolated C. botulinum strain resembled a referenc e strain of North American origin. It did not match any C. botulinum s trains isolated from the Baltic sea-bottom or from the fish caught in the area indicating that the fish was contaminated by C. botulinum in Canada. The conditions resulting in toxin production could not be iden tified. The safety problems associated with vacuum-packaged hot-smoked fish seem to be of utmost concern and the product is one of the most important botulism food vehicles processed on an industrial scale. Tem perature monitoring and the use of time-temperature indicators are to be recommended in order to ensure adequate storage temperature from pr ocessing through to consumption. Allowing the use of nitrate and nitri te together with sufficiently high NaCl concentration in this particul ar product should also be considered. (C) 1998 Elsevier Science B.V. A ll rights reserved.