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roundtable: the evolving enemy Watch Show 4:
"The Evolutionary Arms Race"
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How concerned should we be about becoming infected with resistant bacteria from foods like chicken, beef, and even aqua-cultured fish that may have been grown on diets treated with antibiotics? Will eating less of these foods, perhaps by switching to "organic" chicken, reduce our risk, and do vegetarians have a reduced risk for this reason?
If the use of antibiotics in a widespread fashion at low doses in agriculture, particularly in the raising of animals, is so common and yet so potentially dangerous from the standpoint of evolution of resistance, why is it still the practice? What are the costs and benefits of this practice?
Several people have submitted questions not about antibiotics, but about all of the liquid soaps that are now for sale in supermarkets that are labeled "antibacterial." Do these work like antibiotics in causing further resistance? If so, how, and if not, how is their action on bacteria different than just plain soap?
Americans now seem to be getting fanatic about sterility, and people are trying to raise their children in an almost "germ-free" environment. We have a question from a woman who says that she has several friends, young mothers, generally, who seem to overuse antibacterial products. She asks: Is it not true that the presence of some "germs" in moderation is actually good for the development of our immune system?
In one of the programs in the Evolution broadcast series, there was the story of the leafcutter ants that culture Streptomyces bacteria on their bodies and seem to use those bacteria to apply antibiotics to keep their fungal farms parasite free. This has been inferred to mean that somehow the Streptomyces and the antibiotics they produce have been evolving with the enemy, and this is a kind of use that appears to have been going on for 15 million years without permanent resistance being developed. Is there anything we can do to put ourselves in that situation versus the more static situation we're in now?
Could you give an explicit description of how evolutionary theory informs integrated pest management? I think the cross-fertilization here between bacteria and antibiotic resistance and agricultural pests and insecticide resistance is very interesting, and I don't think many people make that connection.
Some physicians, who are quite impassioned, say they would like to prescribe fewer antibiotics, but their patients demand them. Since in effect they cannot be absolutely positive there isn't a bacterium involved, when, say, a parent brings in a young child who is ill, and they can't be absolutely certain that there won't be bacterial complications as a result of a viral illness, they would like to know how the public will be educated and who is going to take on the job, so that patients will basically get off the doctors' backs and let their colds run their course.
Another part of that question is that doctors are afraid of being sued if they don't prescribe an antibiotic and a bacterial infection does develop. So from the medical perspective of overuse of antibiotics, how might we address this basic problem in the interface between healthcare providers and the consuming public?
   

 

Q: Americans now seem to be getting fanatic about sterility, and people are trying to raise their children in an almost "germ-free" environment. We have a question from a woman who says that she has several friends, young mothers, generally, who seem to overuse antibacterial products. She asks: Is it not true that the presence of some "germs" in moderation is actually good for the development of our immune system?
Panelist Responses: < back to intro page
Stuart Levy
I'll take the first stab because we've been doing some work on this, but the answer is yes. It comes under a cute little term called the hygiene hypothesis. The hypothesis is basically that if there's too much hygiene, too much cleanliness, mainly in the case of infants and young children, that their immune system does not get exercised. You know, you try to exercise your muscles and make them stronger and get your bones to grow. Well, no one is thinking about the immune system, but it needs to be practiced, too, and generally, in its young stages, it needs to encounter certain microbes that help it to turn itself on in a correct fashion.

The history of this idea is kind of interesting. When the Iron Curtain fell and researchers, especially the pulmonologists, went into eastern Europe to look at the effects of air contamination, they expected to see high rates of allergies and asthma, because industries were right next to the cities. And they discovered, to their amazement, that allergies and asthmas were actually statistically much less common in eastern Europe, where there was more air pollution, than in the other industrialized countries. Clearly air pollution was not the answer. So they started looking at other factors. They realized that in Eastern Europe children tended to spend more time in day care from an earlier age, where they were exposed to lots of other children and the microbes they carried. They found that children who lived on farms and spent a lot of time around farm animals had less allergies than those living in the cities.

And what emerged was the finding that there was an overzealous focus on cleanliness. A piece of toast falls on the ground, throw it away. A hot dog falls on the grass, don't even wash it off, throw it away. I mean, these kids didn't have a chance to see the microbes that they need, and so when their immune system sees things that are normally benign it has an abnormal response, which produces asthma, allergies, and so forth. I did see that segment in the Evolution broadcast series with the researcher from Germany, and I think there are many other studies like this going on throughout the United States and Europe, showing that a little bit of dirt is important. And of course, that's a hard message to get across: How can you be too clean, or just clean enough? I think we need recognition of the fact that if we just wash with soap and water and don't have on hand all these other chemicals, which are eliminating some of these helpful bacteria, we're better off.

So I think that this is certainly not a demonstrated harm caused by overuse of antibacterial products, since the previous studies were done before the antibacterial craze, but certainly another potential effect. And I now worry that this use of antibacterials in the home, along with the overuse of antibiotics in kids, is going to create a generation of children that we're going to see -- and we're not going to see it until years from now -- that are going to be allergic and have all sorts of allergy problems. We don't need to. We don't have to wait for these problems to appear before we go back and say, "That was a mistake." I think we should do it right now, because we don't need these antibacterial products.
George Beran
What you have just said is extremely important. And what you are describing, and that takes years to show in humans, is the same thing that we are seeing in animals as well, in livestock and pet animals, only that with their shorter life we see these things sooner. You're really on a very important track. Many food-borne organisms, for example, have very short periods of reproduction. And if you raise livestock in essentially sterile conditions, and then you transport the animals off of this confinement system, they immediately get exposed to these organisms in the trucks. Then you unload them in the packing plant, in the case of hogs and cattle, and they immediately get exposed again, and they may then be contaminated at higher level -- not just may, they are contaminated then at higher levels -- when the meat comes out into the cooler.
Stephen Palumbi
One of the things that this brings up, in addition, is that we tend to focus, when we talk about bacterial populations, on the infectious ones, the deleterious ones, and in fact, we know very little about the normal community of bacteria that is associated with us for our entire lives, inside and out. All the animal species that we raise and the entire environment is a sea of complex bacterial communities. One of the things that you don't find much research published on is the impact of that bacterial community diversity on disease and epidemics and the epidemiology of the transmission of disease.

That's one area that I wonder whether the rest of the panelists could comment on. Is there a trend towards more interest in normal bacterial communities, and do you see that as something that we'll need to know a lot more about in the future?
Stuart Levy
I think that it has been very difficult for researchers to get funds to work on normal, non-disease-causing bacteria. The National Institutes of Health, after all, make it a mandate for any grant that you have to show a health benefit. I think as we produce more evidence that the commensal -- that is, the harmless -- bacteria are critical to certain life processes such as the maturation of the immune system -- and I'm fascinated with what George had to say about animal welfare and reproduction, and it doesn't surprise me -- then I think some of the researchers will get funds.

Think about how poor the funding is for ecology, microbial populations, communities. But I know your field is marine biology, and that certainly has demonstrated how normal microbial communities help in the maturation of fish and other animals. And we should take note of that. Why should it be any different for us? We all live in a sea of bacteria, only a fraction of which do we actually know. We can culture very few of them.

If we were to be raised in a sterile environment, would we not see tremendous changes in the kinds of persons we would be? The answer is yes, because we have evolved in a bacterial world, and that evolution, as we learned from the evolutionary biologists in simpler systems, it is a mutual thing. You do one thing, I do another, but we get along. I think in politics we ought to take note of that; maybe we would evolve more peace than war.

But personally, I think that unfortunately not enough attention and research dollars are going into this area. I will say that there are certain private foundations that are looking at this. The Joyce Foundation, for instance, funded the Alliance for Prudent Use of Antibiotics to look at the ecology of antibiotic use in animals, and their report will be out in a couple months. And I think that that's where a lot of the efforts are going, to look at the impact of antibiotics, not just on the recipient of the antibiotics, but on the whole communities outside. That concept has got to be pushed further in anything we do.
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