The problem with developing new antibiotics is that pharma wants to sell them at a high price to recover research costs. But older antibiotics are out of patent

The problem with developing new antibiotics is that pharma wants to sell them at a high price to recover research costs. But older antibiotics are out of patent an are dirt cheap. So the new antibiotics only make sense in the limited cases where no old antibiotic works. So pharma finds itself selling into a small market that is hard to sell to, because antibiotic resistance is unpredictable. That's why there's a perennial problem of no new antibiotics. The problem isn't the science, it's the economic system of our system of medicine.