AVIR: Like, we also give them to animals. I don’t know why that never occurred to me. But if I had to ask you, like, of all the antibiotics given in the US, what percentage would you say go to humans versus animals?

SOREN: I don’t know. I feel like it’s one of those things we’re not supposed to guess bigger than I would think. But I have no idea. Half? I don’t know.

AVIR: It’s reasonable, but actually 70 percent of all the antibiotics given are given to animals, not humans.

SOREN: Another way of putting that is that every year here in the US, we humans take about seven pounds of antibiotics, whereas farm animals are given 30 million pounds every year. So basically, cows and pigs and chickens are getting four times the amount of antibiotics that we humans are getting.

AVIR: Yeah, I had no idea.

SOREN: Wow!

AVIR: They are basically just mixing their food with antibiotics. They mix the water. They’re drinking water with antibiotics. They, like, spray it on the ground. They inject them with antibiotics. It’s just like a real …

SOREN: So—but this is not, like, just if they get sick.

AVIR: No, no, no. This isn’t just if they get sick. It’s just very willy-nilly. In many cases, these are the same antibiotics that we use, treating, like, the same infections that we get.

SOREN: So Avir ended up talking to a scientist, a guy named Lance Price. He’s the founding director of the Antibiotic Resistance Action Center at George Washington University. But before he was that, he was researching this exact problem, the use of antibiotics on farms. And the thing that he was specifically trying to figure out was: What effect could the use of all these antibiotics on farm animals have on us?

AVIR: So he designs a study, and like all good studies, it involves poop.

SOREN: Of course.

AVIR: It’s like a common theme in Radiolab, I feel like.

SOREN: Yes, it comes up a lot.

AVIR: So he designs this study. All right, so what he does, he decides to study the poop of chicken catchers—the person who goes around the chicken farm, and picks up the chickens by their necks with their hands and throws them in the chicken truck when they’re, like, ready to get harvested, basically. So they’re touching a lot of chickens. So what he does is he measures the bacteria in the poop of these chicken catchers versus the bacteria in the poop of, like, regular people like, you know, you and I.

[ARCHIVE CLIP, Lance Price: So we cultured all this poo, and then we analyzed the data. And the one thing that popped out, like, really strong was gentamicin resistance. And so it turned out that the chicken catchers had 32 times the risk for carrying gentamicin-resistant E. coli as their peers.]

AVIR: So basically these chickens, before they even hatch, they would poke a hole in the egg and inject that egg with gentamicin. Then the chickens would grow up, they’re being fed gentamicin, like, left, right, center. And so the E. coli that live in the gentamicin were eventually learning from this, becoming resistant to the gentamicin. Those bacteria were jumping from the chickens onto the hands of the chicken catchers, into the mouths of the chicken catchers, enough to the degree where they’re literally shitting out resistant bacteria.

[ARCHIVE CLIP, Lance Price: And look, if you’re an epidemiologist and you get three times the difference, you’re doing cartwheels down the hall, right? So you’re like, “I found something! Look at this, it’s miraculous!” But this was 32 times, and I just said we’ve gotta be doing something wrong, right? So we looked at the numbers over and over, and—and it was—it was clean.]

SOREN: So the person handling a chicken is 32 times more likely to have a resistant form of E. coli in their bodies than someone who’s not handling a chicken?

AVIR: Yeah, exactly. And then—then they find out that okay, these chicken catchers are going home, that resistant bacteria is getting into their children. Then they find that those bacteria are spreading through the schools of the children. They later find out that if you’re driving behind that chicken truck carrying chickens, those bacteria are getting off of the truck in through your air vents and landing in the cars behind them onto the people behind it. It’s like—it’s truly insane, and then when you really just sit back and think about it, like, then these chickens go die, they get packaged up with the bacteria in them and they get sent to, like, all of our houses, really.

Thanks: Radiolab