All useful antimicrobial agents are toxic substances. For maximum protection of patients, the concentration of the preservative shown to be effective in the final packaged product should be below a level that may be toxic to human beings based on the recommended dosage of the medicinal product. This test assesses the effectiveness of the antimicrobial agents in a sample when challenged by specific microorganisms dictated per USP <51>. Challenge organisms selected for this test are based on likely contaminants:
• Candida albicans (ATCC No. 10231)
• Aspergillus brasiliensis (ATCC No. 16404)
• Escherichia coli (ATCC No. 8739)
• Pseudomonas aeruginosa (ATCC No. 9027)
• Staphylococcus aureus (ATCC No. 6538)
The sample is inoculated and growth is monitored for about 30 days based on the requirements in USP <51>.
The results of this test are reported on a Pass/Fail basis determined by the reduction of challenge organisms and sample type.