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5 December 2013 11:26 am ,
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An animal rights group known as the Nonhuman Rights Project filed lawsuits in three New York courts this week in an...
Researchers have been hot on the trail of the elusive Denisovans, a type of ancient human known only by their DNA and...
Thousands of scientists in the Russian Academy of Sciences (RAS) are about to lose their jobs as a result of the...
Dyslexia, a learning disability that hinders reading, hasn't been associated with deficits in vision, hearing, or...
Exotic, elusive, and dangerous, snakes have fascinated humankind for millennia. They can be hard to find, yet their...
Researchers have sequenced and analyzed the first two snake genomes, which represent two evolutionary extremes. The...
Snake venoms are remarkably complex mixtures that can stun or kill prey within minutes. But more and more researchers...
At age 30, Dutch biologist Freek Vonk has built up a respectable career as a snake scientist. But in his home country,...
- 5 December 2013 11:26 am , Vol. 342 , #6163
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Resistance Without Antibiotics
28 August 2001 7:00 pm
Antibiotic resistance, an increasing medical problem that renders drugs useless, is mainly caused by overexposing bacteria to antibiotics. But that's not the only way. Researchers have now found that bacteria can become resistant to a host of antibiotics through exposure to a toxin from another bug.
In many environments, bacteria wage a continuous war against each other. Some species fight with an antimicrobial peptide called a microcin to which they are resistant themselves. A team led by microbiologist Steve Carlson at the U.S. Department of Agriculture's Agricultural Research Service lab in Ames, Iowa, was interested in harnessing microcins as antibiotics but wondered whether bacteria would eventually learn how to evade these too. To test this, the researchers used two bacteria that both live in the gut: a strain of Escherichia coli that secretes microcin 24 and a Salmonella enterica strain that is susceptible to it.
The researchers grew Salmonella in a petri dish, then added E. coli. As reported in the August issue of Applied and Environmental Microbiology, the Salmonella quickly developed defenses to the E. coli microcin. But it could also withstand a wide variety of antibiotics like ampicillin, chloramphenicol, tetracycline, rifampin, and even ciprofloxacin, a heavy-hitter used as a last resort against resistant Salmonella. The explanation, the team figured, could be that the microcin turned on the so-called multiple antibiotic resistance system, a pump that some bacteria use to get rid of almost anything harmful. Their hunch proved right: By disabling the pump, they could prevent Salmonella from becoming resistant.
A worrying implication is that bacteria may acquire resistance even when antibiotics are used prudently or not at all, says Carlson--although it's not clear how often this happens.
The study also casts doubt on researchers' plans to employ special killer bacteria to combat infections, says microbiologist Herbert Schweizer at Colorado State University in Fort Collins, such as the use of microcin-secreting E. coli to treat Salmonella infections in chickens. If they induce general resistance, Schweizer says, such bugs may well do more harm than good.