[bayesian_horse]

I've heard the opinion that most antibiotic resistance genes don't seem to originate in agricultural use.

High AB usage is one factor in developing and spreading resistance, but it's way more complicated. For example the resistance genes also have to jump onto a bacterium that is pathogenic...

[tempguy9999]

> I've heard the opinion that most antibiotic resistance genes don't seem to originate in agricultural use.

Maybe true but I don't see the post you're replying to saying that. If you are saying that, a reference to some research showing that would be welcome.

> but it's way more complicated

surely true, but it doesn't mean antibiotic overuse isn't a damn good starting point for resistance to develop.

[bayesian_horse]

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4380918/

[tempguy9999]

This does not back up your claim. Much of it is about lack of evidence on which to draw conclusions. That's clear enough just in the abstract. I'll quote from the abstract. Selectively due to length, but I'll try to be fair:

"The three mechanisms considered are as follows 1: direct infection with resistant bacteria from an animal source, 2: breaches in the species barrier followed by sustained transmission in humans of resistant strains arising in livestock, and 3: transfer of resistance genes from agriculture into human pathogens. Of these, mechanism 1 is the most readily estimated, while significant is small in comparison with the overall burden of resistant disease. Several cases of mechanism 2 are known [so it's been demonstrated to happen], and we discuss the likely livestock origins of [some bacteria] it is hard to assess in robust fashion. More difficult yet to study is the contribution of mechanism 3, which may be the most important of all."

To summarise, a little, some known, and we don't know.

From the summary, and again I'm quoting selectively so be warned:

"The limited data available make it hard to quantify the relationship between antibiotic use in animals and the occurrence of clinical resistance. As we have shown, while there is considerable evidence associating antimicrobial use in agriculture with resistant pathogens in livestock and in the food supply, the evidence for human health risks directly attributable to agricultural antibiotics runs the gamut from speculative to scant"

Summary: possible real threat, too little data to evaluate.

Further, again from the conclusion:

"Once these [antibiotic-resistant] strains have emerged, it might be only a matter of time before they cross the species barrier and adapt to living in humans, at which time there is very little regulation of agriculture can do to prevent their persistence in the clinical setting. The greatest value of reducing agricultural antibiotic use now may be in maintaining a status quo that, while far from ideal, is greatly preferable to the alternative."

Summary: we scientists don't know but we have reason to be very concerned.

These are my selective quotes and my interpretations, but I personally don't see that they support your position.

[bayesian_horse]

TL;DR: I read the article mainly as saying basically John Snow knows nothing.

Up to this point the link between agricultural AB usage and human pathogenic infections with resistant strains is quite theoretical and has relatively weak evidence.