@LouraLoura
"I wonder, does anyone know if the antibiotics in farmed animals actually reach us in a way that will alter our resistance ? And if so, why does no one seem worried about this?
It isn't something I've looked into, so will have a search - sadly the internet throws up too many conflicting results to make much sense of things."
It isn't about the antibiotics reaching us, or about our resistance. The antibiotics force the evolution of bacteria which are resistant (to the antibiotics used).
So then if we become infected with bacteria, there are no antibiotics which can treat them.
Basically, mutations (mistakes in their DNA) happen when bacteria reproduce. Only occasionally, but given how often bacteria multiply, there will be quite a few mutated bacteria out there.
By complete chance, some of the bacteria will have a mutation which means they aren't easily killed by, for example, penicillin.
If you treat the host animal with penicillin, the "normal" bacteria will be killed off. But the mutant bacteria will remain. And then they will reproduce, with no competition from any "normal" bacteria.
So what started out as a population of millions of bacteria, only a handful of which were resistant to penicillin, grows back to a population, which all (or almost all) are resistant to penicillin.
This absolutely is a huge problem. Antibiotics which are used to treat humans, are becoming ineffective due to routine use in farmed animals.
People (such as the World Health Organisation) ARE worried about this. But it is difficult to get industry to change, as feeding antibiotics (for example in drinking water) can help animals to grow bigger and quicker.