THE INTRODUCTION of antibiotics into clinical medicine about a decade ago has revolutionized medical practice. These invaluable agents are now among the most commonly used drugs. It has been estimated that in 1948 the production of penicillin approached 62 tons,1 and it may be suspected that about 5% of this quantity was used on proper clinical indication. The large-scale, indiscriminate use of antibiotics may well be associated with the increasing incidence of drug-fast infections which fail to respond to therapy with any single antibiotic, even when it is employed in very large doses. This type of clinical problem is illustrated in the following case (Fig. 1). REPORT OF A CASE A 38-year-old housewife, with a history of rheumatic fever in childhood, consulted a physician because of amenorrhea for two months. The physician found her pregnant and, because of a loud systolic murmur, recommended a therapeutic abortion, which was performed