Typical preservative challenge assays, such as USP 51, run for 28 days. Microchem can conduct a 7 day test to give product developers early insights with regard to product preservation.

Preservative Challenge "Quick Test": Procedure at a Glance

Antimicrobial preservatives are substances added to non-sterile products to protect the product from microbiological growth that may be inadvertently introduced during the manufacturing process. In this study, the test demonstrates the effectiveness of the antimicrobial protection. 

For the preservative challenge "quick test," the product is inoculated with five different organisms as follows:

  • Candida albicans
  • Aspergillus brasiliensis
  • Escherichia coli
  • Pseudomonas aeruginosa
  • Staphylococcus aureus

The test product is typically inoculated with a concentration between 105 to 106 CFU/ml. Immediately after inoculation the test product is assayed to determine the microbial concentration at “time zero”.  The test product is again sampled at day 7 and assessed for surviving microorganisms.  The performance criteria is set by the Study Sponsor, though Microchem Laboratory generally recommends bacterial kill of >4Log10 within 7 dayss  The test may be modified to include additional microbes according to the Sponsor's needs. 

Test controls are implemented into the study to account for any variables that could affect the test outcomes.  Test controls performed in the study are; assay of the concentration of the germ used to inoculate the test product, viability control of test medium, neutralization control, and media sterility.  The assay of the microorganism confirms the concentration is within the acceptable range, the viability control confirms media isn't toxic to the test germs, neutralizing controls validates that the neutralizing recovery medium stops the bactericidal activity of the test sample.

Preservative Challenge "Quick Test": Microchem's Expertise

Microchem developed the preservative challenge quick test to meet the needs of product developers on tight timelines.  The laboratory is qualified to do the precise dilution and plating required to ensure accuracy, as well as to help clients interpret results.

Microchem Laboratory Is:

An EPA and FDA GLP-compliant testing organization staffed by skilled, experienced microbiologists and chemists.  Microchem can help speed your project to completion.

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