Some principles in the chemotherapy of bacterial infections.
The classification of antibacterial drugs into bactericidal and bacteriostatic groups is of clinical value. Bactericidal drugs are to be preferred when possible as they are more rapidly effective, may be synergistic when used in combination against bacteria difficult to eliminate, and are less likely to leave residual "persistent" organisms. Antagonism between chemotherapeutic agents is of little clinical importance.The modes of action of antibacterial drugs are reviewed. The penicillins, cephalosporins, and cycloserine interfere with bacterial cell wall synthesis. Polymyxin, colistin, and nystatin affect the bacterial cell membrane. Protein manufacture by the bacterial ribosome is interfered with by the tetracyclines, chloramphenicol, erythromycin, and lincomycin, and the initiation of protein molecules by streptomycin. Streptomycin, kanamycin, and neomycin also cause the ribosome to manufacture warped proteins. Nalidixic acid, griseofulvin, and novobiocin upset the D.N.A. replication of the bacterial chromosome.Many of the factors adverse to the success of chemotherapy are unimportant when powerful drugs are given in large doses to relatively fit patients infected with highly sensitive bacteria. But these factors become important when patients, particularly debilitated patients, are infected acutely or chronically with some of the more obstinate bacteria. Some grasp of these principles is therefore both intellectually satisfying and clinically useful.