February 23, 2009
Dangerous Bacteria Present in Norwegian Seawater
Source of Article: http://www.thefishsite.com/fishnews/9207/dangerous-bacteria-present-in-norwegian-seawater
NORWAY - While working on her
doctorate, Anette Bauer Ellingsen
discovered potentially disease-causing vibrios (Vibrio cholerae,
V. parahaemolyticus and V. vulnificus)
in Norwegian seafood and inshore seawater.
Anette Bauer Ellingsen studied the occurrence of potentially pathogenic
vibrios in Norway. These species include the
cholera bacterium (V. cholerae) and the
lesser-known species V. parahaemolyticus
and V. vulnificus. All of these species
may cause disease in people who eat raw or lightly-cooked seafood, and they
can also cause extremely serious wound infection.
V. parahaemolyticus is one of the most
common causes of food poisoning, due to the Japanese predilection for sushi.
In the USA,
food poisoning caused by this bacterium is primarily associated with eating
oysters. Vibrio vulnificus
is also associated with oyster eating, and this bacterium causes the greatest
number of deaths from seafood poisoning in the USA.
That these bacteria also occur in Norway was previously unknown,
and this is the first time that V. cholerae
and V. vulnificus have been isolated from
the Norwegian environment. All of the three vibrios
were demonstrated in Norwegian mussels (at fewer than 100 bacteria /gram) and
in Norwegian seawater (up to 30,000/litre) during the course of the study.
They were first and foremost demonstrable when the water temperature rose
and "not so dangerous" forms
It's important to emphasise
that there can be big differences in pathogenicity
within a species. Both V. cholerae and V.
parahaemolyticus have their
"dangerous" and "benign" variants, based on the toxins
they produce. All V. vulnificus are
assumed to be more or less equally dangerous, primarily in people with
predisposing illnesses such as diabetes or hepatitis, and for people with
Part of Anette Bauer Ellingsen's
work was to investigate whether the "dangerous" variants of V. cholerae and V. parahaemolyticus
occur in Norway.
None of the cholera toxin-producing variants of V. cholerae
were found among the Norwegian samples. However, it was discovered that some
of the V. parahaemolyticus bacteria
produce a toxin liable to cause diarrhoea.
The study showed that the danger of food poisoning posed by vibrios in Norwegian food products is extremely small. Nonetheless,
toxin-producing V. parahaemolyticus was
demonstrated, so one should be careful when eating raw or lightly-cooked
seafood, for example, oysters.
activities and sore infection
In fact, the greatest risk of infection from vibrios is not food. There is possibly a greater chance
of being infected in connection with recreational activities such as swimming
or handling marine fish and shellfish in periods with high water temperature.
All of the bacteria that were discovered during this study are liable to
produce serious wound infection, especially in people with reduced immunity.
The study was carried out under the auspices of the Norwegian School
of Veterinary Science, The Norwegian Food Safety Authority and the The Fishery and Aquaculture Industry Research Fund.
Anette Bauer Ellingsen B.
Sc. (hons) defended her thesis, entitled "Vibrio parahaemolyticus,
V. cholerae and V. vulnificus
in Norway, with special
attention to V. parahaemolyticus", on
December 22, 2008, at the Norwegian
School of Veterinary