View Full Version : E. coli vaccine -- a good idea?
11-08-2001, 09:57 AM
E. coli grows in your colon and the stomachs of cattle. A news article yesterday say that trials are now underway to vaccinate cows so they don't develop E. coli and so it won't poison your hamburger meat or leak into the local water. Seems to be a good idea... but E. coli develop in your stomach and help prevent the colonization of more harmful bacteria, although other people may not appreciate your E. coli in their foodstuffs. My question is, if you kill cow E. coli, will something more harmful take its place... is this really such a good idea?
11-08-2001, 11:07 AM
It would depend if they haven't found any useful purpose for E. coli. It must have some environmental benefit. What do you think? Plus, just getting rid of it in cattle won't do a thing about the huge human amount of it.
11-08-2001, 12:20 PM
Wow, Dr.! My very question/thought, as I heard the story on radio while driving.
My gut instinct(sorry) is to say it's a bad idea. E. coli seems to be such a benign thing unless handled sloppily. We always seems to have greater problems when we try to get rid of a multi-thousand-year-old disease/parasite/bacterium/natural species.
Patiently waiting for Qadgop or some other authority.
11-08-2001, 12:27 PM
Sounds more like a GB than a GQ. I'm with Dr. Paprika. E coli where it belongs is beneficial. It prevents the colonization of harmful bacteria. Eliminating it would, however, prevent urinary tract infections. It's wierd how the bacteria does no harm in the intestines, but plays havoc elsewhere. Perhaps Dr. Paprika will explain how this is possible.
11-08-2001, 03:53 PM
Doc if the intent is only to vaccinate the animal's rumen (stomach) then there's no problem here.
The stomachs of cattle are huge microbial fermenters, absolutely chock full of various bacteria, fungi and protoaoa. If you remove one species then it will certainly be relaced with something else, but it won't be something new, it will just be replaced with one of the thousands or potentially millions of different species already known to inhabit cattle rumens. Since these are already present they are already a factor in our meat processing and as such present no new problems.
The work on the rumen vaccines hass been prompted by an attempt to remove the methanogenic bacteria and so eliminate the greenhouse gas output of cattle. The technique has recently been perfected and AFAIK involves using the urea secreting glands in the animal's mouth to secrete anti-microbials into the rumen. This would have no effect at all on the microbial content of the rest of the gut. This is fine because methanogenic bacteria primarily live in the rumen. If we apply the same tecnology to E. coli then it wouldn't affect colon populations and there will be no risk.The gut flora of the colon of cattle is unknown territory to me so I can't really comment.
Doc we really need a link on this one to see if they're just planning on rumen vaccination or trying to eliminate the bug from the entire gut, which AFAIK isn't possible.
And doc, did I read you right: E. coli growing in human stomachs? I was under the impression the stomach was pretty sterile due to low pH/high protease levels and that normal bugs couldn't grow there (though obviously they can survive and slip through to the duodenum where they can grow). I was under the impression any bacterium growing in the stomach was a bad thing.
11-08-2001, 06:20 PM
I'm certainly no expert on microbiology, hence the question. Certainly it is worth testing in clinical trials. I know E. coli grows mainly in the large bowel in humans -- I said human colon, but later used stomach when "gut" might have been a better word. The stomach is very acidic, hence researchers were very surprised in the late 1980s when it was shown that bacteria like Heliobacter pylori could actually survice there, and contribute to ulcers and adenocarcinomas.
My understanding is that the human colon is colonized by much more virulent bacteria in the absence of E. coli. This may matter even if they were present before since clinical symptoms are often a function of the number of bacteria present, not just their presence. As few as 100 Shigella bacteria cause severe diarrhea, you need roughly a million E. coli to cause a urinary tract infection. Some types of E. coli cause much more severe disease than UTIs, of course.
11-08-2001, 06:44 PM
Well, sorta. All I can say is that Dr_Paprika's concern seems totally justified to me. Gaspode has a valid point about the other bacteria in the gut, but I would want to see a goodly amount of data on the microbial populations of vaccinated cows before I felt good about using it. I would assume that such data would be required before approving the vaccine for widespread use.
As for this:
It's wierd how the bacteria does no harm in the intestines, but plays havoc elsewhere.
There are a couple of answers. Firstly, the dangerous strains of E. coli do play havoc in the intestine. They make certain proteins not found in other strains that allow them to infect the cells of the intestinal lining. This prompts an immune response, destroying those cells, leading to problems.
Secondly, lots of bacteria cause problems when they're outside of their normal environment. Colonization of the blood systems, for instance, by any species, is called sepsis, and is one of the very few emergency life-threatening microbial conditions.
11-08-2001, 07:03 PM
The difference between rumens and the human gut is their function. E. coli is not capable of producing cellulase AFAIK (can any microbiologist correct me?). A such it is basically an accesory organism in the rumen and its loss would be of little consequence. Secondly we're talking here about an active fermenter. It's designed as a fermenter and fertilised deliberately by the animal. Their are always going to be microbes, squillions of them. E. coli isn't a major player, so if we're talking only the rumen no major problems with other nasties taking over the function. E coli is the primary microbe found in human colons so removal would have some interesting effects, but it's not significant in the rumen. If it is only the rumen they're planning on vaccinating there shouldn't be any change to the flora of the rest of the gut. Worrying about the effect on the rest of the gut seems to me to be a bit like worrying about the effect on the gut of removing E. coli from an open wound.
11-08-2001, 07:35 PM
I read in Reuter's health news a couple of years ago that part of the problem with E. coli is the rich diet that modern cattle are fed. The grain-heavy diet produces a more acidic intestinal environment, which in turn produces acid-resistant E. coli strain. This strain is more likely to survive in a human stomache.
According to this article, some of the problems with E. coli could be solved by feeding cattle hay for two weeks before being sold.
[/marginally on topic]
11-08-2001, 08:11 PM
Originally posted by Gaspode
E. coli is not capable of producing cellulase AFAIK (can any microbiologist correct me?).
No, that's right.
E. coli isn't a major player, so if we're talking only the rumen no major problems with other nasties taking over the function.
Do you have any cites on that? It's not that I doubt you, it's just that I'd like to see some numbers on what's found in the average cow.
If it is only the rumen they're planning on vaccinating there shouldn't be any change to the flora of the rest of the gut. Worrying about the effect on the rest of the gut seems to me to be a bit like worrying about the effect on the gut of removing E. coli from an open wound.
Couple of things here - firstly, if they're only planning on vaccinating the rumen, how do they plan on doing that? I can't think of a mechanism offhand that would allow you to activate the immune system in one section of the gut but not in others.
Secondly, the OP stated that the purpose of this vaccine is to eliminate E. coli contamination of ground beef. Logically, to do that, you'd have to eliminate all of the E. coli in the whole cow. Again, I'd like to see some numbers, if any have been published, before speculating on how big an impact that woule be.
11-08-2001, 09:50 PM
Well we have Insignificant numbers of human intestinal organisms are found in the rumen (http://www.bact.wisc.edu/Bact330/lecturenf). SInce E. coli is the major human intestinal bacterium that sounds like it's not present in large numbers.
Then we have Veterinary advice was that the flora and pH in which this material is digested is quite different from that of the intestines where the E.coli O157 is likely to be found (http://www.scotland.gov.uk/library3/health/ecoli-08.asp).
That's all I've got at the moment. My comments are based largely on the fcat that in my entire life I've never seen Escherichia assiated with the rumen flora. If it was significant I'm sure it would have cropped up somewhere.
As for how they can vaccinate the rumen, the version I've heard for methanogen vaccination (and the exact techque is still pretty hush hush) is that it utilises the slaivary system of ruminants. These critters pump gallons of salive an hour into the rumen to keep it moist. If you can provoke and maintain an immune respose this saliva carries the antibodies into the rumen and voila.
I don't know how they could vaccinate the entire gut. Any antibodies from the stomach would be digested in the duodenum and I can't think of any other way to get antibodies into the lumen. Dr Paprika said stomach so i just assumed it was someone attempting to diversify on the methanogen vaccination technique. That's why I asked for a cite. It's a little hard to discuss this when we don't know the details.
11-08-2001, 10:12 PM
I don't think these detils were given in the report I saw on the news.
11-08-2001, 10:39 PM
Everyone should note that they're not vaccinating against all E. coli, just one potentially dangerous strain so actual numbers won't change and their won't be any problems with nastier critters replacing good old E. coli.
That link seems to answer most of the questions. As discussed in one of those links O157:H7 doesn't really occur in the rumen so it's obviously the intestine they're working with. The hint might be "showed the vaccine can work by preventing the bacteria from colonizing in cattle" so maybe they're just using the rumen vaccination to prevent this particular strain from entering the intestine.
11-09-2001, 06:50 PM
Ooooooohhhhh!!! Well then. Hell, yeah. Vaccinate away.
11-09-2001, 07:16 PM
I'd still like to see trials showing the vaccine specifically does target only a few strains. But the details included in the links weren't in the snippet I heard. And there are other E. coli strains that cause damage apart from "Hamburger disease" which are found in cows.
11-09-2001, 10:04 PM
Originally posted by Dr_Paprika
I'd still like to see trials showing the vaccine specifically does target only a few strains.
Me too. And I'd be extremely surprised if the government doesn't require them.
And there are other E. coli strains that cause damage apart from "Hamburger disease" which are found in cows.
True, but O157:H7 is the only one that can kill. Except for the occasional oddball that dies from other strains because the planets are aligned wrong or something.
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