Antimicrobial Susceptibility Tests: Testing Methods and Interpretive Problems

Abstract

Infectious diseases are a leading cause of morbidity and mortality in hospitalized patients. This fact places a tremendous burden on the clinical microbiology laboratory to diagnose rapidly the etiologic agent(s) responsible for a patient’s infection and provide therapeutic guidance for eradication of the organism(s). Laboratories are asked not only to perform these tasks with precision and rapidity, but also in a cost-effective manner in an era of increasing emphasis on reduction of laboratory expenses. Physicians will pose the question — How accurately can antimicrobial susceptibility tests predict clinical outcome? At the same time, the microbiologists ask — What method should we use for performing susceptibility tests? What is the most accurate method? What is the most cost — effective method? What are the limitations of the in vitro tests? I will try to address these questions in the following discussion.