Bacteria and handling

[Crusty]

There is a current discussion on the "other" forum that goes further to what I discussed earlier about the quality and accuracy of the information provided.

This was in response to a document uploaded that reference handling procedures to reduce bacteria risk. http://www.ctahr.hawaii.edu/oc/freepubs/pdf/FST-38.pdf

I am quite confused as one chap says, "fish are cold blooded and can't host or transmit e-coli". He has said this twice that I know of without any reference, which seems to be contrary to the following information.

This doc says fish do carry E.coli:
http://periodicos.uem.br/ojs/index.p...File/2007/1487

In the present study, the most common species found in the gastrointestinal tract of Nile tilapia belong to eight Gram-negative bacterial species: Aeromonas hydrophila, Aeromonas veronii, Burkholderia cepacia, Chromobacterium violaceum, Citrobacter freundii, Escherichia coli, Flavimonas oryzihabitans, and Plesiomonas shigelloides. The presence of various organisms which are potentially pathogenic to humans, in fish alimentary tract, is suggestive; its significance in initiating human diseases, unknown. However, the presence of potential human pathogens suggests that fish either improperly handled, undercooked or consumed raw may cause various diseases to susceptible individuals.

This one also suggests fish carry E.coli though it is introduced from an external source.
http://www.d.umn.edu/~rhicks/lab/Hansen%20et%20al%202008%20JGLR%2034.pdf

Geldreich and Clarke (1966) showed that fecal coliforms and Streptococcus faecalis could be found in fish intestines. They speculated that fecal coliforms are not part of the permanent microflora in fish, but their presence is caused by polluted water and is influenced by feeding habits.

Another document that is more relevant to aquaponics:
http://sos-planet.org/documents/aqua...ood-Safety.pdf

Cool and coldwater aquacultural production occurs at temperatures that are generally below 18oC. Warmwater aquacultural production occurs at temperatures higher than 18oC, and includes temperatures as high as 30 oC. In surveys of bacteria present under aquacultural conditions, Salmonella spp., E. coli and other potential enteric human pathogens, although rare or in very low numbers when present, are most often found in warmwater aquaculture rather than in coldwater environments.

Can anyone clarify this for me please?

[Shayne]

Hi Crusty,

Came across this the other day which also suggests that E.coli only comes from warm blooded animals and any E.coli enters via contamination.

http://www.aquaponicsjournal.com/art...A.htm#Question 5

Most articles i can find seem to suggest that fish can be carriers of E.coli in their intestines most likely from contamination with warm blooded animal feces but they may not survive or thrive very well in the fish???

http://www.seagrant.umn.edu/news/2008/07/02

Cheers Shayne

[Crusty]

Thanks Shayne.

In this doc you posted (thanks for that)
http://www.seagrant.umn.edu/news/2008/07/02

"Fish probably acquire E. coli when they eat food contaminated with feces," said Hicks. Researchers don't expect E. coli to flourish in cold-blooded fish, since the bacterium is more common in warm-blooded animals. "However, it is possible that fish may reintroduce E. coli bacteria into waterways when they excrete their own waste,"

There is no real consensus regarding E.coli and fish, as they are most definitely carriers and I agree it would need to be introduced, which would not be that hard. Once introduced, especially in warm water aquaponics/aquaculture, I "would think" it will thrive in warmer climates. How is it introduced, perhaps from the fingerlings brought in from pond culture? The primary thought I had, was I see many people with their fish food sitting in containers outside or at least not refrigerated. This would be an entry point for bacteria. I doubt it is of any real risk in the UVI example as they remove their solid waste (poop) prior to the raft subsystem. What may be of minor concern is gravel beds where there is a large build up of organic waste which is a great place for the bacteria to thrive. I still think it is good practice to have hygiene in mind when handling the food produced in the back yard, especially those that ferment the fish waste in the grow beds.

[GaryD]

Hi,

The presence of rats (and their faeces) around aquaponics systems is a likelihood in many places. I remember visiting one system where the rats were stealing the tomatoes from the grow beds (the smell of decaying fish waste probably attracted the rats in the first place).....and the owner had baits set all over the place. One half-grown rat actually expired on the ground while we were looking around.

The reason I mention this story is that, regardless of whether the fish have eColi or not, it may well be present on your vegetables because of the movement around the system by rats or mice......and that this would be virtually impossible to prevent.

Washing food before you eat it is always a good idea.

Gary

[Shayne]

Hi,

In my system I would think the source which would have greatest potential for E. coli contamination would be from birds. Both fish pond and growbeds (except for 1 in a greenhouse) are outdoors and my water comes from rainwater collected from the roof. That being said my traditional soil veggie beds used to be where the growbeds are now and i used the rainwater on them with the addition of a range of warm blooded animal manures worked into the soil. So i figure the possibility of E.coli is probably no greater than the soil based system (maybe less)??? But strangely enough i think i take greater care in washing the veggie from the aquaponic system than i did from the soil system??
Cleaning of the fish is probably more important with care needed when removing the stomach and intestines as that is where E.coli is likely to be if anywhere.

Cheers Shayne

[GaryD]

Hi Shayne,

In my system I would think the source which would have greatest potential for E. coli contamination would be from birds.

A useful point.......any system in the open would face the same risk.

While not wishing to undermine the need for appropriate washing of vegetables (or for appropriate personal hygiene), I'm much more concerned about the chemicals in our environments than the germs.

Gary