Much of the emerging evidence is that while the amount used in livestock makes for flashy numbers, it's likely medical overuse in humans is the main driver of the problem.

Recent mini-thread on it by Marc Lipsitch, a Harvard epidemiologist who does a lot of work in the area: https://twitter.com/mlipsitch/status/1206419839872569346

Including use in urban poverty: https://www.nytimes.com/2019/04/07/health/antibiotic-resista...

Where antibiotics are handed out without prescription and people live in squalid conditions.

"70 percent of salmonella infections in Kenya had stopped responding to the most widely available antibiotics, up from 45 percent in the early 2000s."

"Even when the drugs are authentic, many poor Kenyans try to save money by buying just a few tablets instead of the full course — not enough to vanquish an infection but enough to allow bacteria to mutate and gain resistance."

The current population of Kenya is 50m, forecast to increase to 95m by 2050, and 156m by 2100.

Kenya also currently has the scientific output of Serbia, a country 14% the size. Its likely that Kenya will continue to import drugs developed in advanced nations, and internally produce only antibiotic resistance.

https://www.natureindex.com/country-outputs/generate/All/glo...

SO I do a little work in Kenya, and it's really hard there. Because you do have rampant resistance, but you also have lack of drug availability - especially in rural parts of Kenya.

We've got some data suggesting there that stewardship is, relatively speaking, less impactful there than decreases in transmission. Because the environment is heavily contaminated, which is itself conducive to the spread of resistance.

Back in 2017, the FDA banned the use of medicinally important antibiotics in livestock.

https://www.cdc.gov/drugresistance/food.html

This line item for allowed uses from that link:

* Prevent disease in animals that are at risk for becoming sick

Is pretty much a giant loophole.

If those animals are treated, they then need to be pulled out of the food supply until the antibiotic washes out.

It’s not in a farmers best interest to use an antibiotic in those circumstances unless the animal needs it.

>until the antibiotic washes out.

This is part of the problem. If animals are given the antibiotics, then their waste products contain them, and piles of manure or water runoff/storm drains/wastewater ponds form a giant evolutionary experiment for development of drug resistant organisms.

They're not just a problem while they're in animals, they're a problem if they're used at all.

Apparently, most antibiotics don't undergo metabolism in animals, and 40-90% of ingested antibiotics in livestock are excreted in urine and feces[1].

Those antibiotics go on to contaminate groundwater, and as you say, contribute significantly to antibiotic resistance[2].

[1] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4220964/

[2] https://en.wikipedia.org/wiki/Antibiotic_use_in_livestock#An...

That’s often irrelevant. If a cow is going to be slaughtered at 36 months, you can use antibiotics for 95% of their lifetime and still have a 50 days window at the end.

> until the antibiotic washes out.

while I don't want surprise antibiotics in my food, I'm probably more concerned about the antibiotic resistance that antibiotic exposure generates. The flora of those animals _will_ have drug resistance genes that doesn't just "wash out". That resistnce can be passed to other animals or human by direct contact, environment or otherwise.

Does that make any practical difference for animals meant for consumption like beef cattle, hogs, or chickens? You can give them all the antibiotics you want until a few days before slaughter.

It does. The animals will be colonized by bacteria that have "learned" to deal with all those antibiotics you gave. That resistance is easily transmitted.

I understand the problem with antibiotic resistance, but telling a farmer that an animal treated by antibiotics can't enter the food supply until after treatment ends doesn't really solve the problem when it comes to animals raised as food -- the farmer can treat the animal with antibiotics for nearly all of its life, only stopping the treatment just before slaughter.

Totally agreed. I'm naive to much around Ag/Husbandry. If that's what farmers do, that is a concern. From a microbiology point of view, the concept that "washing out" the drug before slaughter improves anything is flawed. It will be a reservoir of smoldering antibiotic resistance as long as that practice persists.

That's good to know, thanks for the link. However, up until recently, you could buy 55-gallon drums of antibiotics without a license on sites like Alibaba.