[Prospect of chemotherapy in the 21st century]

"Golden Era in Chemotherapy" has begun with the discovery of penicillin in the early 1940's and lasted for two decades during which many antibiotics were discovered. However, the once-believed bright prospect that every infectious disease could be eliminated on the earth by the discovery of antibiotics had to be canceled owing to the emerging of drug-resistant microbes. It was indeed a rat race. We are now at the point when we have to seek another way to combat infectious diseases: One possible way might be not to eradicate the microbes but to coexist with them so long as they do no harm to the human hosts. The first step of infection with pathogens to the host is the adherence of the microbes to the surface of host cells. Therefore, the method how to inhibit this adhesion of microbes to the host cells may provide a new tool to prevent the development of infectious diseases without elimination of microbes from the host. This is just an example of strategy by which humans and pathogens coexist at peace and should be taken into consideration for the development of new-type antibiotics or "anti-infective drugs" in the 21st century. The analysis of genome sequences has been accelerated recently for various pathogenic bacteria one by one. New targets in the pathogenic microbes for the development of new antibiotics can, therefore, be determined from the genetic point of view. The discovery of antibiotics has indeed been the history of collection of innumerable species and/or strains of bacteria from the soils to search for the biologically active anti-pathogenic agents. The current progress in the technology of molecular genetics, however, will certainly make it possible to search for active molecules by DNA technology; bacterial DNA but not whole microorganisms from the soil is to be transformed into the conventional bacteria and searched for active molecules with combat against pathogens.