Growth Promotion and Negative Controls – Does Shipping Affect the Results?

Why Growth Promotion?

USP Chapter <61>, Microbiological Examination of Non-sterile Products: Microbial Enumeration Tests ,there is a requirement for the testing of Growth Promotion (GP) for each batch of medium as well as testing for Negative Controls (NC).  Growth Promotion must be tested for each new batch of nutritive broth.  The purpose of the GP Test is to determine the suitability of the culture media for the growth of target organisms.  The medium is challenged with a small number (not more than 100 cfu) of microorganisms to assure its nutritive properties.

USP Chapter 61USP Chapter <61> lists the following acceptance criteria for liquid medium: “Liquid media are suitable if clearly visible growth of the microorganisms comparable to that previously obtained with a previously tested and approved batch of medium occurs.” It is recommended to use parallel testing; in parallel testing the new medium and the previously approved medium are inoculated with the same microorganism suspension, by the same technician, using the same method and same environmental conditions.  The only variable is the medium. GPT is performed by inoculating the product with ? 100 CFU of microorganisms, defined by the pharmacopoeia.

BioLumix Quality Assurance and Certificate of Analysis

For every batch of vials prepared by BioLumix a thorough testing, including growth promotion and negative controls, is done.  Growth promotion is tested performed, for each organism, by inoculating 4 vials of the new lot and comparing the detection time (DT), and amplitude of the curve to a lot that previously passed the PG. At least 2 different strains of organisms are used in each media.  Additionally at least one negative control organisms is tested and compared to the reference.  In the growth control assay the DT of the new lot has to be within a range of 50-200% from the reference vial.  A certificate of analysis is issued with each lot of vials.

Is there a need to redo GP and NC after shipping the vials to the end users?

In other words, does the shipping of the vials to the end users influence the GP and NC of the vials? The study described below was undertaken to answer this question.  BioLumix vials are always shipped UPS second day air.  The furthest destination in the USA is California.  The study was conducted by double shipping second day air to California and back.

Summary of Validation Data

Methodology-Quadruplicate vials that were shipped to California and were returned from there where compared to vials that stayed in the lab. This test was performed on three different lots of media, using three different media types (Total Aerobic Count, Enterobacteriaceae, and Yeast and Mold Vials).

Results-The data shows that the shipped vials and the vials that stayed in the laboratory results of the test show identical growth curveshad identical growth curves, falling close to each other.   There is no difference in growth promotion or negative control between vials that were shipped (actually double shipped) and vials that stayed on the shelf for any of these lots, as can be seen from the attached example.  The example compares the curves of total aerobic count vials (TAC) inoculated with Bacillus spizizenii var subtilis ATCC 6633, shipped to vials that remained in the laboratory (Key: Shipped vials: Purple, Yellow, Beige and Dark Green; vials that remained in the lab: Dark Blue, light Green, Light Blue and Red lines). As can be seen from this example the Curves are indistinguishable

Similar results were obtained for all three lots of TAC inoculated with Bacillus spizizenii var subtilis ATCC 6633; Escherichia coli ATCC 8739; and Staphylococcus aureus ATCC 6538;

A buffer was used as a negative control for the TAC vials, and no difference was seen for all three lots between shipped and vials that remained in the lab.

Similar results were obtained with combined yeast and mold vials (YM) inoculated with Aspergillus brasiliensis ATCC 16404; Candida albicans ATCC 10231; Saccharomyces cerevisiae ATCC 9763; and Staphylococcus aureus ATCC 6538 (SAT1) as negative control.  There is no difference in growth promotion or negative control between vials that were shipped and vials that stayed.

The shipping experiment was also conducted with Bile-Tolerant Gram-Negative Bacteria vials (ENT) inoculated with Escherichia coli ATCC 8739; Salmonella enteritidis subsp. enterica serovar enteritidis ATCC 13076; Citrobacter freundii ATCC 8090; and Staphylococcus aureus ATCC 6538 as a negative control. There was no difference between the data generated by the system for shipped vials, as compared to vials that remained in the laboratory.


The data shows that the shipped vials and the vials that stayed in the laboratory had identical growth curves, falling on top of each other.   There is no impact of shipping on growth promotion or negative control.  The results validate that there is no reason to perform again the growth promotion and negative controls after shipping to the end user. The C of A supplied with the BioLumix vials is indicative of Growth Promotion and Negative Control followed the shipping.