We must not forget, too, that one of the problems with the use of antibiotics was their routine use in some countries for disease prevention in animals being raised for food consumption. I believe (confirmation or denial requested) that in some places (USA suggested) that cows were producing milk containing traces of antibiotics which had been routinely administered to prevent mastitis.
I think that Rhiannon is correct in stating that as the genomes of various bacteria are becoming better understood that new forms of antibacterial drugs are being engineered. We must hope, for future generations, that these are used appropriately and not enthusiastically overused as antibiotics have been in the past.
As Sir Henry Harris put it succinctly in 1998:
Without Fleming, no Chain or Florey; without Florey, no Heatley; without Heatley, no penicillin.
Yet while Fleming, Florey and Chain jointly received the Nobel prize for their work in 1945, Heatley's contribution was not fully recognized for another 45 years. It was only in 1990 that he was awarded the unusual distinction of an honorary Doctorate of Medicine from Oxford University, the first given to a non-medic in Oxford's 800-year history.
Alexander Fleming is rightly celebrated for his serendipitous discovery of penicillin, but it was Florey's Oxford team who really produced the workable drug. And then Churchill's wartime government gave it freely to the Americans to produce commercially. Americans then tried to claim that penicillin was an American achievement.