The Resistance Crisis

Fleming himself warned in his 1945 Nobel Prize speech that bacteria would develop resistance if antibiotics were misused. He was right.

Bacteria evolve resistance through several chemical strategies: producing enzymes that destroy the antibiotic (like beta-lactamase, which breaks penicillin's core ring), modifying their ribosomes so the drug cannot bind, or developing efflux pumps that eject the drug before it works.