PDA Journal of Pharmaceutical Science and Technology published 2017
Geobacillus stearothermophilus spores on stainless steel discs are routinely used as Biological Indicators (BIs) for the validation of hydrogen peroxide bio-decontamination
Given ongoing concerns about the reliability and response time of BIs, we explored the potential for an enzyme-based approach decontamination process evaluation. Thermostable adenylate kinase (tAK) enzyme was coated onto a solid support and exposed to hydrogen peroxide vapour, in parallel with standard commercial 6-log BIs, during a series of vapour-phase hydrogen peroxide (VPHP) cycles in a flexible film isolator. The exposed BIs were enumerated to define the degree of kill at different time intervals and the results compared to the tAK values, as determined by measuring ATP produced by residual active enzyme.
Both BIs and the tAK indicators exhibited a biphasic inactivation profile during the process. There was significant variance between individual cycles, with some cycles showing complete inactivation of the BIs to the limit of detection of the assay, within 6 minutes, whilst BIs in some cycles were inactivated at a time greater than 12 minutes. The log-kill of the BIs at intermediate time points were plotted and compared to the fully quantifiable measurements derived from the tAK indicators at the same time points.
The results demonstrated very similar inactivation profiles for the enzyme and for the BIs, thus it was possible to define a relationship between relative light units (RLU) measurement and BI kill. This indicates that it is possible to use tAK measurement as a direct measure of VPHP bio-decontamination performance, expressed in terms of log reduction. Since tAK measurement can be achieved within a few minutes of VPHP cycle completion, compared with a minimum of 7 days for the evaluation of BI growth, this offers a potentially valuable tool for rapid VPHP bio-decontamination cycle development and subsequent re-qualification.
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