Compliance with NCCLS approved standard M22-A2 for bacteriologic media quality assurance: a survey of 124 Ontario microbiology laboratories.

Objective: The purpose of this QMP-LS patterns-of-practice survey was to determine quality assurance (QA) processes used in Ontario for purchased and in-house culture media, and compliance with recommended practices.

Methods: QMP-LS required laboratories to submit copies of media QC records for August to October 1998. Target media were blood agar, chocolate agar, MacConkey agar, sorbitol MacConkey agar (SMAC), Campylobacter agar, and selective media for pathogenic Neisseria spp. Procedures for acquisition and maintenance of QC stock cultures, media-type specific QC strains, time and temperature of incubation, and the test inoculum were required. Data were captured and analysed using Microsoft Excel.

Results: Marked variability and inadequacy of media QC records of 124 participating laboratories was noted. 12/124 prepared media in-house, most did not comply with NCCLS QA recommendations. Those purchasing prepared media frequently did not comply with NCCLS recommendations. In-house QC was not performed by 9% for chocolate agar, 87% for MacConkey agar without crystal violet, and 53% for SMAC agar. Recommended ATCC strains were used by less than half of participants. Time and temperature of incubation of the QC plates were not always appropriate. Only 65/117 laboratories used a correct inoculum to test the sensitivity and selectivity of media for pathogenic Neisseriae. Physical characteristics of prepared media were rarely recorded. Most laboratories were not aware of their supplier's QC protocols.

Discussion: Few Ontario laboratories comply with the NCCLS recommendations for QA of culture media. Major compliance failures were not performing QC at all, inappropriate choice of QC bacterial strains, and inoculum used. Incomplete record keeping was common and methods for maintaining stock cultures were sub-optimal. External quality assessment of this important parameter of microbiology practice needs to be undertaken on an ongoing basis.