I’ve written here a couple of times before about the possibility that well-intentioned efforts to improve hygiene, by using anti-bacterial agents, and to cure disease, by using antibiotics, may be contributing to the rise in microbes that are resistant to many drugs, and also to the decline in beneficial microorganisms. The risk of this seems especially high when the antibiotics or disinfecting agents are used improperly. It is clear that the use of these agents creates selection pressure for drug resistance among bacteria, but less clear why that resistance seems to develop so rapidly.
Now, some new research, reported in an article in Wired Science, seems to show a new mechanism by which bacteria can develop resistance to antibiotics, which perhaps explains why that resistance can develop relatively rapidly.
A newly discovered mechanism of antibiotic resistance helps explain how bacteria have so quickly undermined medicine’s front-line defenses, turning miracle drugs into duds in just a few decades.
In a paper published in the journal Molecular Cell, researchers describe how the presence of antibiotics produces an increase the organism’s production of oxygen free radicals. These highly reactive agents damage bacterial DNA. The bacteria’s damage repair efforts tend to produce a larger than normal number of mutations in its DNA. The presence of the antibiotic of course creates selection pressure in favor of those mutations that lead to resistance; but because many mutations are generated, it is in effect possible for the bacteria to acquire resistance to several drugs at once.
“You have a wide range of mutations being introduced across the genome. Some afford resistance to that antibiotic. Some afford resistance to other antibiotics,” said James Collins, a Boston University biomedical engineer who described the mechanism in a paper published Feb. 11 in Molecular Cell. “It would happen anyways, but this process is accelerating it.”
In essence, in addition to its other effects, the presence of the antibiotic “speeds up” the evolutionary clock for the bacteria.
Infections caused by antibiotic-resistant bacteria are a serious public health problem. This is an important bit of research, which hopefully will help us better understand the process by which resistance is developed.
What do you think of agricultural antibiotics, or broad-spectrum antibiotics in the food chain? It seems that we’re getting a little tetracycline every day with our dairy and meat products, and perhaps others as well. That could go some distance towards explaining drug-resistant bugs and also, with the effect on intestinal flora that are supposed to be there, the rise of things like ulcerative colitis and Crohn’s disease.
I think the routine addition of antibiotics to animal feed is almost criminally stupid. We are in the midst of conducting a large, uncontrolled experiment on ourselves, and I have a feeling we’re not going like the results, for all the sorts of reasons you’ve mentioned. The evolution of some degree of antibiotic resistance is inevitable — the mutagenic effects described in the article, plus natural selection, will see to that. But we sometimes seem hell-bent on accelerating the process.
I would make one distinction: I don’t have a problem with using antibiotics on animals to treat actual disease, but with their indiscriminate use to make the animals grow faster (=cheaper).
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