STARTING WITH THE discovery of antibiotics by Alexander Fleming in 1929, the last century has uncovered an unprecedented number of cures for human diseases, including STDs. As a result, the fatality rates for STDs such as syphilis and gonorrhea have plummeted.

Significant advances have also been made in the diagnosis and treatment of many STDs. Yet, in spite these successes, the number of people infected with STDs has never been higher, and the emergence of AIDS has made STDs one of the fastest-growing and most wellfunded focuses of medical research.

There are good reasons for seeking new and more effective treatments for STDs. One is the appearance of new strains of drugresistant organisms against which previously successful treatments have less and less effect. Because bacteria are extremely adept at transferring their drug-resistant abilities to their drug-sensitive neighbors, antibiotic resistance is occurring...