The discoverer of penicillin warned of antibiotic resistance before it was ever a crisis

Accepting the 1945 Nobel Prize for discovering penicillin, Alexander Fleming warned that giving patients too little of the drug, or stopping treatment too early, could let the hardiest bacteria survive and multiply into a strain immune to it entirely. Resistant bacteria did exactly that in the following decades, and antibiotic resistance is now considered one of the biggest threats to modern medicine — exactly as Fleming predicted before a single resistant infection had ever been recorded.

— Alexander Fleming, Penicillin (Nobel Lecture) — Nobel Prize in Physiology or Medicine, 1945