[Microbiologic principles of antibiotic therapy].

Antibiotic therapy, in contrast to other drug treatments, is aimed at the etiology of a given disease state. The main basis of antimicrobial chemotherapy is thus identification of the causative pathogen and documentation of its susceptibility to the least toxic antibiotic. However, these requirements are frequently impossible to meet in everyday management of infections. In many situations, therefore, decision-making in antimicrobial chemotherapy must be based on a "best-guess" diagnosis regarding the causative pathogen and its susceptibility to the antibiotic. The process of decision-making in antimicrobial chemotherapy for the single most frequent infections encountered in outpatients is discussed, and the pertinent antimicrobial treatment for these infections (pharyngo-tonsillitis, otitis media, sinusitis, bronchitis and urinary tract infections) is outlined.