In his splendid memoir, Lewis Thomas movingly describes what must have been the prevailing optimism at the time. Bacterial infections had been a tremendous scourge for young and old alike, and physicians had become accustomed to watching helplessly as patients succumbed to community-acquired infections caused by Streptococcus pyogenes, Staphylococcus aureus, Streptococcus pneumoniae, and Mycobacterium tuberculosis. In relatively short order, however, therapeutic failures due to the emergence of antibiotic resistance were recognized. Patients whose tuberculosis had responded to streptomycin therapy returned months later with progressive disease due to streptomycin-resistant M. tuberculosis. Resistance to penicillin in Staphylococcus aureus spread rapidly, and within a few years more than 50% of nosocomial Staphylococcus aureus isolates were penicillin resistant.