General concepts on the chemotherapy of infectious diseases.

Chemotherapy affects both the host and the microorganism. Antimicrobial agents have a profoundly adverse influence on the surrounding environment if they are improperly employed. In all chemotherapy, it is critical to know what the infecting organisms are, and if that information is not immediately available, to base chemotherapy on those organisms that characteristically produce the infection. It also is critical to have an understanding of the distribution of antibiotic-resistant microorganisms in one's community if the proper antimicrobial agent is to be selected. The host's status and site of the infection will impact upon the choice of drug. Infection in sites in which phagocytic function is poor, such as in heart valves or in the spinal fluid, or in individuals lacking complement, white blood cells, or immunoglobulins, must be treated with bactericidal agents. An understanding of the pathogenesis of infection caused by different microorganisms will provide insights into the type of therapy, duration, and amount of drug that must be used. Ultimately, the chemotherapy of infection should be based on integration of the activity of antimicrobial agents with their pharmacologic properties.