Preservative efficacy testing: considerations and areas for savings

By Joseph Heinzelmann

Often one of the first questions we receive about the BioLumix system is “how much does it cost?” While this blog post won’t be able to cover specifics on the costs of the BioLumix system or the individual tests, it will outline some of the considerations and areas for savings as it relates to preservative efficacy testing according to the United States Pharmacopeia <51>.  In our example analysis, we are able to reduce the cost of doing PET by nearly 40%.

USP <51> helps show the effectiveness of a preservative, or a preservative system. This testing is done according to the procedures outlined in USP Chapter <51> Antimicrobial Effectiveness Testing. This chapter describes in detail which organisms to use, the appropriate inoculum based on a product, and the necessary log reductions that the preservative system needs to achieve.

Before getting started on a comparison of protocols, we have to make sure a suitability study has been performed. The following link describes how suitability can be performed: http://www.mybiolumix.com/the-importance-of-suitability-testing/. The experts at Neogen can help you with your suitability testing questions.

Before a side-by-side comparison is done, a validation is required of any alternative method. Using the protocol outlines in USP chapter <1223> Validation of Alternative Microbiological Methods we can see that the BioLumix system meets the following requirements: Specificity, Limit of detection, precision and repeatability, robustness ruggedness, false negative rate, and false positive rate. A more in-depth discussion around USP validations and Neogen’s Validation book can be found here: http://www.mybiolumix.com/biolumix-validation-book-for-dietary-supplements/

An overview of USP <51> can be found here: http://www.mybiolumix.com/guidelines-simplified-automated-microbiology-testing-system. The two methods can be broken down into two approaches; materials and labor. Comparing the materials is straight forward. Reviewing the protocol shows that each time point requires an analysis of 3 bacteria, 1 yeast and 1 mold. Each organism requires a neutralization, and multiple dilutions when using traditional microbiology. Each organism also requires a total of 5 plates! Each plate requires a dilution blank, as well as a pipette tip.


There are several points of parity between the USP <51> traditional plate count methodology and the BioLumix system. First, the BioLumix system also requires 3 bacteria, 1 yeast, and 1 mold to comply with USP <51>. Each method will also test the preservative system at multiple time points over the course of 28 days. However, the BioLumix system is able to provide a microbiological count without 5 plates, without multiple dilution blanks, and without multiple pipette tips. The picture below helps illustrate how a nearly 40% reduction is achieved with Neogen’s BioLumix system methodology.

The second comparison is to determine the amount of labor required to run a USP <51> protocol with traditional methods. With the automation of the BioLumix system eliminates plate reading. The vials in the BioLumix system are automatically read, and the result is recorded in the database. Report writing is simplified with the Certificate of Analysis generated automatically. Time study estimates performed by Neogen estimate the labor reduction using BioLumix for PET is greater than 60%!

The BioLumix system is great for additional quality testing according to USP chapters 61 and 62. The advantages of BioLumix for this application has been covered in a recent blog post: http://www.mybiolumix.com/the-relevance-of-usp-methodology-in-microbiology-in-pharmaceuticals/.

Learn more by asking our experts for a cost breakdown, suitability analysis or additional information by contacting the author or our microbiology experts.