Selection of antimicrobial agents for routine testing in a clinical microbiology laboratory.

Each clinical microbiology laboratory must establish its own standard battery of antimicrobial agents to be tested routinely on clinical isolates of various organism groups. Some choices are based upon the intrinsic activities of antimicrobial agents for a particular group of organisms, for example, agents primarily active against either Gram-positive or Gram-negative bacteria. For final selection of limited batteries of agents for routine testing, however, it is necessary to use additional criteria based upon physician prescribing patterns and the availability of antimicrobial agents in a particular institution. A fundamental principle in the selection process should be routine testing and reporting of those antimicrobial agents that physicians actually use, that is, the institution's formulary agents. Testing of the most appropriate drugs for an institution may be complicated by lack of availability of some antimicrobial agents among the standard panels offered by automated instrument or commercial test system manufacturers. The laboratory should develop its final test batteries in consultation with the infectious disease and pharmacy services and the pharmacy and therapeutics and infection-control committees of the medical staff. These choices should not be made based upon the most convenient selection of drugs from the laboratory's perspective or based upon pharmaceutical industry promotional efforts.