Battered cod and chips … how about battered cod and Vibrio’s – Correlation of total Bacterial & Vibrio’s spp. Populations between fish and water in the aquaculture system.
As natural fish stocks decline, but demand increases the need for
aquaculture is greater than ever. Aquaculture systems are highly susceptible to
disease which can have highly detrimental impacts both economically and to
human health. Although the risks of disease in aquaculture is known, very
little is known about the correlation between the water quality and subsequent
bacterial contamination and disease of fish products.
In this study they investigate the degree of bacterial transmission of 3
Vibrio spp.: V. anguillarum, V. parahaemolyticus and V. vulnificu
from the aquaculture water to the fish produce. They did this by challenging
aquaculture systems with the 3 Vibrio’s spp. and then recorded the levels
present in the water compared to those in the fish tissues. The 3 Vibrio
spp. used in this study were deactivated using UV light, this was due to
concern for the health and safety of the scientist involved as 2 of the 3
Vibrio spp. used pose serious threats to human health.
Once the Vibrio spp. were introduced to 3 of the 4 tanks (with one being a
control) the experimental sampling began whereby they sampled the 500ml of
water and the tissues of 2 randomly selected fish of varying species. They
repeated this sampling technique at day 2,4 and 6 of the study which lasted 6
days. They then extracted DNA from both the fish filets and water samples and using
the multiplex real-time PCR assay quantified the Vibrio spp. present and total
bacteria. The methods used in this experiment were taken from Kim and Lee (2014).
The results of this study describe a correlation between Vibrio counts in
the water to that found in the fish’s tissues, it showed increasing Vibrio's in
the water led to an increase number in the fish tissues. However, the longevity
of the Vibrio populations differed between the water and tissues samples, with
Vibrio populations being absent from the water samples by day 6 but still
present within in the fish tissues. The authors suggest a few reasons for this,
firstly they suggest that the deactivated Vibrio’s may have been gradually
removed through the Bio filters in the tanks hence no longer being present in
the water samples. Secondly, it is suggested that in previous studies Vibrio
introduction can triggered the immune response of creating antibodies. However,
in this study it is suggested that a known resistance of Vibrio species to
antibodies may suggest why the Vibrio's are maintained in the fish when no
longer present in the water.
Another possible difference is caused by the deactivated Vibrio’s, it’s
possible that the infection and colonization rate of the fish by the
Vibrio's was possibly lower due to the deactivated state. Linking to this, it
is suggested that due to deactivation the culture methods used were inefficient
for Vibrio and Bacterial counts and even the real time PCR only highlighted
species found above a certain concentration, so this is an area that would need
further development. Another area for suggested improvement is the fact that
different fish species of different ages and sizes were used, and this too may
have had an impact on the results.
Overall this study shows the importance of monitoring in aquaculture and
that monitoring the water for Vibrio spp. could provide a real indicator of
fish health or contamination. It also highlights that the prevention of Vibrio
contamination should continue to remain a priority in aquaculture especially as
the industry continues to grow.
Paper reviewed
Kim, J., & Lee, J. (2017). Correlation of Total Bacterial and Vibrio
spp. Populations between Fish and Water in the Aquaculture System. Frontiers In
Marine Science, 4. http://dx.doi.org/10.3389/fmars.2017.00147
Paper referenced
Kim, J., & Lee, J. (2014). Multipurpose assessment for the
quantification of Vibriospp. and total bacteria in fish and seawater using
multiplex real-time polymerase chain reaction. Journal Of The Science Of Food
And Agriculture, 94(13), 2807-2817. http://dx.doi.org/10.1002/jsfa.6699
Hi Pippa,
ReplyDeleteThank you for this review. The method is neat and straightforward and I am surprised that no one looked at the correlation between water and fish bacterial abundance! Was the day 6 the first day when no bacteria were present in the water? I have a feeling it would be logical to go on with the study for couple more days and see the further changes in bacteria abundance both and fish and in the water; that might help to establish the full dynamics
Thank you,
Anastasiia
Hi Anastasiia,
ReplyDeleteYes I know seems like a fairly simple method but I wonder if it hasn't been looked at before due to the possible risks associated with the species used in the experiment?
I think the continuation of the study could prove interesting but I think what they are implying in the paper is that the Vibrio's in the water are filtered out by day 6 regardless. So after this point although initially the level of Vibrio sp. in the fish increased at almost the same time as that in the water ,once the Vibrio sp. had been transmitted to the fish from the aqua culture water the transmitted Vibrio sp. remained resident in the fish fillet regardless of the levels in the water.
With the authors suggesting the Vibrio species could remain for an extended period of time even after the aqua culture water had been purified.
I guess the only true way to test the full dynamics would be to remove the filter or somehow prevent it from removing the Vibrio sp. to see what would happen if they remained in the water.But I imagine this is pretty tricky in an aquaculture system and would just encourage other microbes and possible pathogens that would interfere with the study.
Hope this answers your questions.
Thanks for reading,
Pippa