STABILITY STUDY AND EXPIRY DATE DETERMINATION OF BAIRD-PARKER AGAR (BPA) MEDIUM PRODUCED AT THE NATIONAL INSTITUTE FOR CONTROL OF VACCINES AND BIOLOGICALS

Abstract

Staphylococcus aureus is a common bacterium found in laboratory animals and may interfere with quality control testing results. Baird–Parker Agar (BPA) is widely used for the isolation and identification of this microorganism. This study was conducted to evaluate the stability and establish the shelf life of BPA medium produced by the Department of Experimental Media. Three batches of BPA medium manufactured in May 2025 were evaluated at weeks 0, 4, 8, 12, 14, 16, 17, 18, and 19. Evaluation criteria included appearance, pH, sterility, and growth performance. Staphylococcus aureus ATCC 25923 and Escherichia coli ATCC 8739 were used to assess recovery and selective inhibitory performance, respectively. The results demonstrated that all BPA batches met the acceptance criteria for appearance, pH, and sterility throughout the 19-week storage period. The selective inhibitory activity against Escherichia coli ATCC 8739 was fully maintained. However, the recovery rate of Staphylococcus aureus ATCC 25923 gradually declined over time and fell below the acceptance criterion (≥50%) at weeks 18 and 19. Based on these findings, the shelf life of BPA medium is proposed to be 4 months from the date of manufacture when stored at 2–8°C.