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How Taking Antibiotics Can Actually Make You More Sick
by Daniel Zwerdling

You eat a hamburger contaminated with salmonella.In your intestines, potentially dangerous salmonella don't have room to proliferate.You take antibiotics that wipe out all kinds of bacteria—except the resistant salmonella. Resistant salmonella take over, making you sick.

There are a few ways that resistant bacteria on food can hurt you.

The most direct way: you munch some chicken that has resistant bacteria on it, the bacteria make you sick, your doctor prescribes antibiotics—and they don't work, so you get sicker than you would have otherwise.

But there's a more complicated—and hidden—way that resistant bacteria can get you. Let's consider salmonella, which is the second leading cause of "food poisoning" in the United States. Researchers at the Centers for Disease Control and Prevention estimate that 1.4 million people get salmonella every year. More than 500 of those victims die.

CDC researchers say it wouldn't be a surprise if it turned out that you have salmonella in your gut right now, which you got from eating a contaminated hamburger or chicken sandwich yesterday. But if you're a typical healthy person, you probably don't have to worry: At any given moment, our intestines are teeming with myriad kinds of bacteria—some are beneficial, some are benign, and some are potentially harmful. But most of the time, all these bacteria live in a kind of ecological harmony, so no single type can dominate—and so the potentially dangerous salmonella don't have room to proliferate, and wrack you with fever and cramps and diarrhea.

But now let's suppose that the salmonella you ate are resistant to antibiotics. CDC researchers say that cases of resistant salmonella have exploded over the past decade, mainly as a result of routine use of antibiotics on farms. Roughly 20 percent of salmonella that they test now are resistant to two or more antibiotics. Some are resistant to more than a dozen different drugs.

And let's also suppose that you have an ear ache or bronchitis, and you go to the doctor, and start taking antibiotics. It's like what the military calls a carpet bombing campaign: those drug "bombs" don't just kill the enemy bacteria causing your ear or lung infection, they start killing lots of the beneficial and benign bacteria in your intestines, too. The antibiotics wipe out all kinds of bacteria—except the salmonella that happen to be resistant.

So the ecological balance in your intestines has been disrupted and the resistant salmonella can take over. And your doctor is baffled: what strange kind of "bug" would have caused an ear ache or a cough, and then suddenly cause diarrhea? The answer: you got sick from two competely different infections —and antibiotics made one of them possible.

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