scope:

The M22 standard provides information on quality control of commercially prepared microbiological culture media to users and manufacturers. M22-A3 is a revision of the approved standard, M22-A2, published in December 1996.

The basic premise of this standard is that the retesting of commercially prepared microbiological culture media is unnecessary for those media that are of proven reliability. The categorization of media that do not require retesting by the user is based on quality control data collected from surveys of clinical laboratories enrolled in the bacteriology proficiency-testing program conducted by the College of American Pathologists (CAP). The media types listed in the M22 standard are well established for recovery of clinically significant microorganisms. Exemption of certain media from routine quality control by the clinical laboratories assumes that media performance is monitored by an overall quality program that correlates test methods with clinical information, and monitors test procedures and specimen quality. Media used for antimicrobial susceptibility testing have different quality control recommendations that are detailed in separate NCCLS documents.

Changes or additions to this newest revision are the following: 1) Designation of the responsibilities of the manufacturer, distributor, and user; 2) clarification of the media included in various categories; 3) simplification of the basic protocols for the maintenance of quality control organisms; 4) incubation conditions for media quality control; 5) recommendations for the quality control of media used for certain fastidious organisms; and 6) expansion of the cutoff for acceptable failure rate from 0.3% to 0.5% and the categorization of an additional 27 media as exempt from user testing.