In vitro testing of antimicrobial agents.

Antimicrobial susceptibility tests provide information that may be helpful in the initial selection of antimicrobials to be used in therapy, may prompt a change in an existing regimen to one including a more active antimicrobial agent, or may allow substitution of one antimicrobial agent with another equally effective but less expensive antimicrobial agent. The clinical value of bactericidal testing is less clear-cut due, at least in part, to methodologic variations and biological and technical variables. Standardization of methods provides both intralaboratory and interlaboratory reproducibility, as well as interpretability of results.