Laboratory quality assurance testing of microbiologic media from commercial sources

Culture media that perform as intended are crucial to accurate work by a clinical microbiology laboratory. As cost-containment becomes an increasingly important pressure in clinical laboratory management, the value of each laboratory performing its own quality assurance testing of media has been challenged if the media are purchased from a manufacturer who is required to perform quality assurance testing. In the past ten years of using commercially prepared media from eight different national and regional suppliers, the authors have encountered an average of six types (15 shipments) of media each year that failed to meet their laboratory's performance criteria, which reinforces the need for clinical laboratories to continue their own performance testing of media manufactured commercially, particularly when the media are used for primary isolation. Quality control testing of media can be performed most cost-effectively by purchasing in the largest lots and shipments that shelf life and storage requirements allow, streamlining test procedures while keeping detailed records of performance characteristics, and purchasing media from firms that have demonstrated competence and integrity.