Public health experts have been warning for years that bacteria are starting to gain on us. More strains of the microbes that are resistant to antibiotics are emerging around the world as people continue to overuse the drugs to treat human infections as well as over-expose animals in agriculture in order to keep infections under control.

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Now officials report that a 48-year-old Pennsylvania woman with a urinary tract infection has been infected with a bacteria that could not be treated with colistin, which doctors usually reserve as a last resort treatment if other antibiotic classes don’t work. Colistin-resistant strains have also been found among cattle and in meat sold for human consumption.

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Fortunately, the E. coli in the woman’s case was vulnerable to other classes of antibiotics, so she recovered. So far, doctors have not reported a bacterial strain that is simultaneously resistant to every single antibiotic class currently available. But that strain could be lurking and ready to emerge at any time as current antibiotic use pushes the microbes to develop mutations that help it to become resistant.

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The appearance of the colistin-resistant strain is concerning because it means that bacteria have already figured out a way to combat the drug; that means more strains could pick up the resistance in coming years. The hope at this point is that the colistin resistance does not merge with resistance to other antibiotics. That would create a superbug that can’t be treated with any drugs now available.

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That’s just a matter of time, public health experts say; they are urging doctors and policy makers to take action as current antibiotic drugs near the end of their effectiveness. Congress has provided $150 million to state and local public health departments to monitor cases such as this woman’s infection, but that’s just a stop gap measure. Drug companies are also working on new classes of antibiotics that bypass the way bacteria can develop resistance, but so far no promising agents are ready for testing.

In the meantime, doctors say the best way to combat resistance is to limit use of antibiotics, especially in agriculture, and to ensure that the medications are only used when necessary to treat human infections. A surprising number of doctors, for example, prescribe antibiotics to treat viral infections for which they aren’t effective.

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