The problem of selecting antimicrobial agents before (or without) the results of susceptibility testing

The appropriate selection of an antimicrobial regimen depends upon more factors than merely the results of susceptibility testing. It is a task more difficult today because of the recent development of many new antimicrobial agents. Clinicians who prescribe antibiotics need to invest time and energy beyond reading a package insert in order to gain familiarity with antimicrobial agents. Understanding the antimicrobial and pharmacologic properties of a few agents from each class of antimicrobial agents will help make the selection of empiric regimens less difficult. Essential to empiric therapy is frequent and habitual reassessment of antimicrobial regimens with possible application of cost-effective modifications kept in mind. Once the pathogen is isolated, the empiric regimen can be modified. The very last factor that is used in modification of the antimicrobial regimen is the result of susceptibility testing. Prior to (or without) this information, the clinical outcome of serious infections most often will depend upon the early institution of appropriate empiric therapy.