Antimicrobial synergism-an elusive concept

Abstract

Synergism is a term that enjoys wide use in medical literature. There is scarcely an issue of any of the major publications that deal with antimicrobial agents that does not contain at least one article on antimicrobial synergism. Despite the widespread use and acceptance of the concept of synergism, there remains a great deal of imprecision in the way in which it is applied. The article by Norden et al. [1] that appears in this issue of the Journal brings this point into sharp focus. The authors of this paper used two standard methods to test the interaction of combinations of antimicrobial agents against a series of clinical isolates of Klebsiella pneumoniae. Unlike some previous investigators, they were unable to find a correlation between the results obtained by the checkerboard titration method (using several schemata of interpretation) and the time-kill curve method. In view of this failure, they concluded that greater standardization of methodology and more precise definition of antimicrobial synergism are urgently needed. Their concerns appear well founded. © 1979 by The University of Chicago.