As a young student studying microbiology at the University of Kentucky, I immersed myself in the study of antibiotic-resistance. When I wrote my Master’s thesis in 1954, I wrote at length about a danger that continues to be a growing threat today: antibiotics becoming ineffective against the evolution of modern disease. Even then, the laws of science were clear. The more often bacteria are exposed to low levels of antibiotics, the greater the chance that some bacteria will evolve and become antibiotic-resistant superbugs. That basic principle of evolution still holds true today. The...