It is quite amazing that the oldest group of medically useful antibiotics, the fJ-Iactams, are still providing basic microbiologists, biochemists, and clinicians with surprises over 50 years after Fleming's discovery of penicillin production by Penicillium. By the end of the 1950s, the future of the penicillins seemed doubtful as resistant strains of Staphylococcus aureus began to increase in hospital populations. However, the development of semisynthetic penicillins provided new structures with resistance to penicillinase and with broad-spectrum activity. In the 1960s, the discovery of...