Disk diffusion antimicrobial susceptibility testing for clinical and epidemiologic purposes.

Antimicrobial susceptibility testing is one of the most important and useful tests performed by the clinical microbiology laboratory. The value of disk susceptibility testing in epidemiology is enhanced by its simplicity of performance, reproducibility of results, and ability to indicate whether a single strain is likely to be the cause of many infections. By using a specific set of antimicrobials for either gram-positive or gram-negative bacterial susceptibility testing and by following recommended testing procedures, laboratories can reliably identify similarities and differences in strains. We propose a list of antimicrobial agents chosen specifically for their value in disk susceptibility testing for clinical and epidemiologic purposes and describe the recommended methods of testing.