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Peer Review Article | Open Access | Published 8th October 2025
Biological indicators (BIs) strategy to use in VHP/vH₂O₂ Bio-decontamination cycle development, performance qualification and ongoing re-qualification
James Drinkwater | EJPPS | 303 (2025) | https://doi.org/10.37521/ejpps30302
Introduction
Biological indicators of Geobacillus stearothermophilus spores, inoculated on stainless steel carriers within Tyvek® primary packaging are used as a challenge of efficacy for a bio-decontamination cycle during cycle development, performance qualification and subsequent re-qualification, typically to verify a VHP/vH₂O₂ bio-decontamination cycle meets 6log sporicidal requirements. Bio-decontamination cycles are a required process to establish Grade A conditions inside barrier technology and further support maintaining conditions as a contamination control measure during material transfers between GMP grades including into Grade A and within surrounding Cleanrooms.
The ideal spore inoculum on a BI carrier is a mono layer, Spore clumping yields Rogue BIs and Failed BI lots; poor quality.
The regulatory expectation and the efficacy performance target for isolators and Closed RABS (if applicable) is a 6-log sporicidal reduction [European Commission]. In accordance with scientific principles, the inactivation of one million spores on a single BI carrier is expected to yield a six-log reduction. Furthermore, VHP/vH₂0₂ is not a sterilisation process (penetrative) and referenced in Pharmacopeia’s as it has penetration limitations however with conditions of low bioburden, absence of protective soiling (including; fatty acids from finger touch, silicon coatings) surface sterility and zero CFU recovery is possible to assure.
However, Geobacillus stearothermophilus spore BIs are notoriously difficult to manufacture as both inoculum purity (clean exposed spores) and spore clumping are a consistent efficacy challenge resulting in in-lot system resistance variability, resistance variations between BI lots and the presence of so called ‘Rogue BIs’ all of which can lead to unexpected BI positives. Rogue BIs are considered as BIs that include localised spore clumping or spores protected by intrinsic contamination as a result of sub-optimal spore inoculation and/or purification steps [Drinkwater et al.].
As a consequence, using a single BI at challenge locations can make it difficult to determine and verify cycle efficacy.
This is because a single positive BI at a challenge location does not provide any clarity on whether the unexpected positive result was due to a BI quality issue or a process efficacy reduction at the challenge location. The incidence rate of Rogues in BI lots is not consistent, which introduces an additional layer of complexity. From time-to-time BI manufacturers and the Pharmaceutical Industry experience BI quality deviations that can significantly impact the efficacy of BI studies in VHP/vH₂O₂ bio-decontamination cycles. It is seldom any BI lot is completely clear of Rogue BIs.
Trending bio-decontamination cycle data over years demonstrated ‘Good quality’ BI lots have Rogue incidence rates at (or less-than) 0.1% - 0.3%. More recently quality deviations up to 1% - 3% Rogue BI challenges have been experienced and managed by set strategies. In one recent case (2025) the BI rogue incidence rate for a BI lot was 6%. Poor quality BI lots, with Rogue incidence rates up to 6% are considered unmanageable resulting in many repeat cycles, including Rogue investigation cycles and confusing datasets that are difficult to justify as qualifying a robust VHP/vH₂O₂ bio-decontamination cycle.
A strategy is required to manage BI quality variations when approaching each cycle development, performance qualification and re-qualification. This strategy starts with the use of multiple BIs placed at challenge locations. Two approaches can be taken:
1) Use of duplicate BIs and the acceptance criteria to deliver data that demonstrates 100% BI 6log sporicidal reduction at all challenge locations.
2) Use of triplicate BIs and application of statistics to support 6log sporicidal reduction at challenge locations, meaning accepting/ justifying some BI positives within a cycle.
Both approaches rule out use of a single BI challenge during cycle efficacy studies as there is no allowance for unexpected Rogue BIs because of BI quality issues (Rogues) or there are insufficient data sets that have any statistical significance.
It follows that the use of multiple BIs at a study location is solely for managing BI quality issues that affect efficacy results.
It is recommended, for any selected strategy, to reduce the impact of sub-optimal BI quality by completing pre-use qualification studies. Such studies can eliminate sub-optimal BI lots and those with high Rogue incidence rates.
Four pre-use BI lot qualification studies should be considered:
System ‘D-value’ study.
BI enumeration – Population count.
Scanning Electron Micrographs (SEM images) to study spore distribution and purity.
Rogue Incidence rate study.
System ‘D-value’ study.
As there is no BIER vessel (Biological indicator evaluation resistometer – test system) for BI efficacy resistance studies applied to gaseous – vapour phase bio-decontamination cycles due to the extent of process variables and bi-phasic nature of VHP/vH₂O₂ (gas and liquid/ condensable vapour phases). Each determined ‘D Value’ only relates to the specific test system used in D value studies as such defined as ‘System D Values’.
The test system is typically a pharmaceutical isolator with a VHP/vH₂O₂ bio-decontamination system that can create specific efficacy conditions. BIs are then exposed in studies with different System D Value methodologies applied e.g. either Survivor curve or Limited Spearman Karber method (LSKM).
Note: the ISO standard ISO11138-series for biological indicators fundamentally applies to BIs used in sterilization cycle qualifications e.g. Moist heat, Dry heat or Gamma irradiation all of which are penetrative processes. In contrast, VHP/vH2O2 applied to Isolators, Closed RABS, Material transfer devices and Cleanrooms is a surface treatment and, in this context, does not deliver sterilization. Hence the guidance from the ISO standard is helpful but not mandatory for BIs applied in VHP/vH₂O₂ cycles, special considerations are required.
Further guidance is provided in the PDA Technical Report TR51, but this guidance focuses on the manufacture of BIs for use in gaseous – vapour phase bio-decontamination cycles, rather than on strategies for managing variations in BI quality before and during use in studies.
System D values, as log reductions, define the time required to inactivate 90% of the spore population. Starting with one million spores on the carrier, the first log reduction (of six) reduces the number of spores to 100,000 and so on: log 2 reduces the number of spores to 10000, log 3 to 1000, log 4 to 100, log 5 to 10 and log 6 to 1. This is followed by overkill, which would achieve conditions of surface sterilisation/ zero CFU recovery on adjacent surfaces to the BI if the surfaces were exposed and free of VHP/vH₂O₂ penetration barriers (e.g. soiling). As a biological system BIs have inherent variability so a target System D value ‘range’ and not a specific ‘value’ is defined in BI purchase or in cycle qualification studies. An appropriate system D value range is 1.0 to 2.0 minutes.
To achieve these System D value results the test system (study Isolator) cycle has to be developed to enable conditions for exposure and BI sampling to be suitable to build a data set that can determine a System D value. Once developed this ‘reference’ VHP/vH₂O₂ cycle is consistently applied in the same test system so the main ongoing variable is BI resistance efficacy which is the subject of study. BI resistance efficacy then can be trended lot to lot so acceptance criteria for pre-use qualifications can be set based on ‘trend data’.
Such System D value studies are completed in Laboratory Study Isolators and typically the type of VHP/vH₂O₂ generation system and target efficacy conditions (Pre-Dew point or post-dew point) are the same as the conditions intended for use e.g. in a production Isolator.
It follows that the System D values developed by BI manufacturers are specific to their test system as a label claim whereas independent System D values are specific to the independent laboratory test system. Therefore, exact equivalence is neither expected nor required. Importantly, as a Quality control measure, limits need to be applied so that variances are accommodated within the appropriate 1.0 to 2.0-minute system D value.
During cycle development within the production isolator, it is not expected to complete System D value studies specific to the production Isolator, as such studies are more appropriate for laboratory test Isolators. System D value studies in a test Isolator support the pre-use qualification of the biological indicators used in cycle efficacy studies in the production setting.
The development of VHP/vH₂O₂ cycles may include BI Kill time studies with timed removal of BIs from efficacy exposure as a performance measure of time to kill at one or two reference locations. However, such studies are not System D value studies. In all cases sublethal studies should be used as part the ‘characterisation’ of efficacy at all challenge locations, so that overkill margins can be set based on data including efficacy at worst case locations. Worst case locations are considered as those that result in the longest time at set conditions to inactivate BIs at the target sporicidal log reduction.
As a quality control measure for BI use in VHP/vH₂O₂ cycle development, performance qualification and re-qualification studies, it is advisable (though not mandatory) to complete independent System D value studies and not just rely on the BI manufacturer’s System D value label claim based on their test system. It is also advisable to use the same BI lot for cycle development and VHP-PQ studies then a single pre-use qualification study can apply. If different BI lots are used, then pre-use qualification studies are required for each lot. Inherently because of expiry dates, different BI lots will be used in re-qualification studies, typically one year on from VHP-PQ studies.
BI enumeration – Population count.
In principle enumeration (counting the number of spores on the carrier) is used to confirm that there are more than one million spores on the carrier, so that the 6-log sporicidal efficacy can be verified when the BI is inactivated. For enumeration studies, spores need to be recovered from the carrier. Because recovery is challenging, with steps including sonication, to assure more than one million spores are recovered from the carrier for counting studies the BI carrier is over inoculated (typically 2-3 million). With an expected recovery rate of 50% in independent enumeration studies, there will still be verification that one million spores are present for the efficacy challenge studies.
If spore populations are over-inoculated, e.g. to 4 million or more, this significantly increases the risk of spore clumping and consequent Rogue BIs. However, efficacy resistance and spore population do not entirely correlate. For example, lower spore populations are more resistant when spores are not exposed. Efficacy remains consistent for spores that are exposed. It is spore clumping, spore protection by intrinsic contamination or encrustation that increases resistance, and this can also apply to lower spore populations.
Scanning Electron Micrographs to study spore distribution and purity.
Although it is not required by the regulations or expected as part of the pre-use qualification of BI lot, scanning electron microscopy (SEM) has been found to be an important quality control check. This helps to manage the risks and consequences of using biological indicators with sub optimal quality, which can result in unexpected BI positives. SEMs also support investigations into unexpected BI growth to assess if the outcome is a BI or process issue.
SEM data is complementary to the other data sets in BI pre-use qualification, the images can be used to access if the spore inoculum is clean, clumped or if there is intrinsic contamination present. It is unlikely that SEMs identify Rogue BIs, as only a small sample set is applied, and the required low incidence rates of Rogues means that the samples are unlikely to contain them (localised highly clumped masses of spores). The following are examples of SEMs that had different outcomes during Pre-use BI qualification studies.
In this spore presentation Fig.1. the surface treatment of VHP/vH₂O₂ (non-penetrative) would not be possible to deliver 100% BI spore inactivation. In this case the System D value was also out of specification.
In this spore presentation Fig.1. the surface treatment of VHP/vH₂O₂ (non-penetrative) would not be possible to deliver 100% BI spore inactivation. In this case the System D value was also out of specification.
There is always a little more confluence (spore grouping at BI carrier edges) but in this case, Fig 2. there was no excessive spore clumping. Therefore, the BI lot was used in cycle development and PQ studies without any problems, other than the occasional unexpected positive. Following an investigation, it was confirmed that the unexpected positive was a Rogue BI.
Unexpected BI positive investigations follow a procedure first to quality the unexpected positive result for further Rogue BI verification studies. Pre-qualifications include a cycle-by-cycle review to confirm the challenge location had no previous BI positives at the same location and any positives are only (1) of the (2) BI challenges at the location. Repeating positives and/or duplicate positives at the same location indicate a localised process efficacy issue e.g. cycle marginality and not enough overkill to cover inherent resistance variability of BIs lots, hence not a BI rogue issue. In the case of Fig 3 (A &B) the Rogue incidence rate was high; 6% with a contributing factor of localised carrier edge spore encrustation.
Encrustation typically results from sub-optimal purification steps to remove BI manufacturing media and vegetative cell debris to achieve clean spores.
Rogue Incidence Rate Study.
Following the first three pre-use BI qualification studies (Enumeration, System D value, SEMs), if the results are acceptable, it is advised to progress to a Rogue Incidence rate study, for which a higher number of BI samples is required.
A Rogue Incidence rate study is conducted in the same study isolator with a qualified and known 6log sporicidal efficacy cycle (with overkill). The purpose of the study is to assess if there are BI positives that were present in an overkill cycle, e.g. Rogue BIs, by placing challenge BIs in one ‘easy to kill’ location with full exposure. The minimum number of BIs that can be applied to complete a Rogue BI incidence rate study is 100. Given the limited number of BI samples, it has to be recognised that, statistically, one BI positive could indicate a Rogue incidence rate of up to 3%. If this is understood, the results can be managed within the Rogue investigation cycles, for example by using triplicate BI challenges at all unexpected BI positive locations (e.g. three locations, then nine BIs). Following the investigation cycle, the expected outcome would be that all nine BIs are negative (no growth).
Increasing the sample set to 300 or more BIs for the Rogue incidence rate study would improve the accuracy of the result, but this would be considered an excessive amount of BIs taken from the Qualification BI lot and is both expensive and provides little added value.
Results indicating Rogue incidence rates of > 3-6% when 100 BIs are used in the study indicate an unacceptably high Rogue incidence rate and call into question the release for GMP Qualification studies, even though system D value, enumeration and SEMs indicate lot acceptance.
Applicability of guidance on managing BI quality issues to ‘Dry Fog’ bio-decontamination
So called ‘Dry Fog’ bio-decontamination process that atomises hydrogen peroxide solution into droplets of 8-12 microns for delivery onto surfaces to effect sporicidal efficacy can be impacted by the same BI Quality issues. However, such a process cannot be directly compared with a gaseous vapour phase bio-decontamination process that this guidance applies to. For Dry Fog some of the BI QC studies may need adaption.
The small molecules of hydrogen peroxide at 10⁻¹² pico size generated by flash evaporation (by heat on a fire bar or hot plate) pass directly through filter media e.g. Tyvek®, HEPA filters whilst Dry Fog droplets at 8-12 micron do not pass directly through. So, the processes apply a different H₂O₂ delivery mechanism to interact with surfaces that in turn interacts differently with BIs (in a Tyvek® primary pack).
Through hydrogen bonding molecules and droplets will form mono layers (deposition/ condensate layers) however the vapour phase processes provide a dynamic interaction of molecules with surfaces and H₂O₂ mono layers and do not rely on a static ‘wetted surface’ e.g. as delivered by manual disinfection application.
Strategies for managing BI Quality issues
The following strategies for managing BI quality issues, including possible Rogue BIs in VHP/vH₂O₂ cycle development, VHP-PQ studies and re-Qualification studies, are based on using BI lots that have completed successful BI pre-Use qualification studies (as listed and discussed in the article).
Strategy 1: Duplicate BIs and acceptance criteria of 100% BI inactivation of 6log sporicidal reduction at challenge locations to verify VHP/vH₂O₂ cycle efficacy.
The use of duplicates provides an opportunity to determine if an unexpected BI positive was a Rogue BI. In this case, only one of two BIs would be an unexpected BI positive, and following review may be considered for a subsequent BI rogue investigation cycle. This review is a precursor to a rogue investigation cycle and includes a cycle trend analysis to determine whether unexpected BI positives are randomly distributed or at a repeat location. In the latter case, a process efficacy issue is considered as the root cause of the BI positive, indicating marginal efficacy at the challenge location.
If the strategy is to verify 100% BI inactivation of 6 log sporicidal efficacy, then one single BI negative result (at each challenge location) supports this acceptance criterion, provided that the duplicate BI alongside it can be verified as a high-probability Rogue. It is not possible to determine if the actual unexpected BI positive was a Rogue because, once incubated, no further study is possible. In this case, ‘Rogue BI verification’ is considered in the repeat investigation cycle with new BI challenges.
To add to the probability and significance, triplicate BIs are exposed in the previous unexpected (Rogue) BI location. With only triplicate BIs at the study location, it is extremely unlikely that one of these three new BI challenges will be another Rogue BI.
If the investigation cycle demonstrates full inactivation of the triplicate BIs at the study location, alongside the original BI inactivated as one of the duplicate challenges, then there is a high probability that the unexpected BI positive was a Rogue. In this case, the original cycle can be accepted without the need for a repeat cycle with BI challenges in all locations. Repeat cycles would be open to more unexpected BI positives and would result in repeated investigation cycles without any added value. All unexpected BI positives should be subjected to a Rogue investigation cycle to verify 100% BI inactivation at every challenge location and provide a complete data set.
With this strategy, it makes no sense to use triplicate BIs challenges at every challenge location, as the more BIs used, the greater the chance of unexpected BI rogue positives. Furthermore, interpreting results 1 of 3 positive and 2 of 3 positive cannot be justified with clarity if the acceptance criteria is 100% BI inactivation at the challenge locations.
Duplicates are enough to support the probability 1 of 2 unexpected positives was a Rogue and investigated for Rogue verification.
Unexpected BI positives should occur at random challenge locations and within the Rogue incidence rates for a single or group of cycles, e.g. repeating VHP-PQ cycles. The more BIs that are used in qualification studies – either by applying triplicates at each challenge location or by a repeating cycle series, e.g. VHP-PQ studies – the higher the potential for Rogue BI positive results, and the greater the extent of investigation cycles required to verify unexpected BI positives as Rogues. Such an outcome is inefficient cycle development, both costly in project time and consumables (BIs and growth media).
Strategy 2: Use of triplicate BIs at all challenge locations and application of statistics to support 6log sporicidal reduction meaning accepting and justifying some BI positives within cycles.
Statistics based on inactivation of spore populations across a number of BIs can be interpreted as 6log sporicidal efficacy [Drinkwater et al.]. In this case to increase the sample size and support the statistical analysis triplicate BIs are applied at each challenge location.
The intent is to use the statistical analysis to justify 6log sporicidal efficacy is achieved that may include some BI positives alongside BI negatives (inactivated BIs) but without any subsequent investigation cycle to determine if the un-expected BI positive(s) was a Rogue. In all cases one of the triplicate BIs must be negative (no growth – inactivated) with acceptance criteria set for interpreting and 1 of 3 BI positives or 2 of 3 BI positives.
The extent of unexpected BI positives would relate to the Rogue BI incidence rate so there would be a lack of confidence process efficacy was robust if there are excessive numbers of locations that demonstrate BI positives, or 6log efficacy cannot be supported by statistics [Eddington].
Such a strategy relies on the user site understanding and justifying the statistics and individual GMP inspectors (regulators) and GMP auditors also understanding and supporting the statistical approach. Accepting cycles that include BI positives is a much more challenging strategy than the alternative strategy of verifying 100% BI inactivation at every challenge location with data-based evidence that any unexpected BI positives are Rogues (highly probable as Rogues).
The Future with BIs and EIs: biological and enzymatic indicators.
For some time, the alternative technology of Enzymatic indicators (EIs) has been studied alongside biological indicators (BIs) during VHP/vH₂O₂ cycle development and PQ studies [Franke et al., Schachtschneider et al., Scharf et al.]. Such is the increase in knowledge (based on results) that EIs are now considered to be able to complement BIs to improve efficacy knowledge at each challenge location, delivering more efficient cycle development studies and saving time. This is because EIs provide data within 30 seconds, whereas BIs require an incubation period before demonstrating results through the growth-turbidity of the TSB growth media.
Importantly, the efficacy of bio-decontamination is determined by sporicidal log reduction, that can be determined for BIs via negative no-growth or positive growth (demonstrated by turbidity in TSB growth media) or log reduction studies. In contrast EIs require correlation studies. EI analysis after cycle exposure in a luminometer provides results as Relative Light Units (RLUs) exhibited by a luciferin-based reaction of remaining enzyme after VHP/vH₂O₂ exposure. Hence RLU numbers require correlation to the log reduction exhibited in biological indicators so RLU data sets can be interpreted for efficacy against as log reduction.
Current best practice (2025) and ‘state of the art’ is that BI to EI correlation studies are required to be completed on the production-scale isolator and cannot be reliably determined in a laboratory test isolator. Data from efficacy at worst-case locations is required as part of correlation studies and that requires the production Isolator or production system to be used in correlation studies.
As EIs are introduced alongside BIs initially to build data sets during cycle characterisation of worst-case locations and associated correlation studies, duplicate BIs are used with a single EI alongside. For subsequent studies, once correlation is completed, one single BI and one single EI can be used e.g., cycle development verification of overkill cycle and VHP-PQ studies. In the case where a single BI positive is found and unexpected in overkill cycles intended as VHP-PQ study parameters it cannot be assumed this was a rogue BI even if the EI data indicates over 6log efficacy.
BI efficacy data (not just EI data) is required in final cycle qualification studies, therefore any BI positive will need an investigation cycle with a triplicate BI challenge at the positive growth location(s) (only) and an expected result of full inactivation (no-growth) after 7 days incubation if the unexpected positive is confirmed to be a rogue. Applying one BI and one EI can then apply the strategy for managing unexpected BI positives during cycle development as Rogue BIs will then be directly supported by EI data. Possibly after a number of successful re-qualification studies, EIs only can be used in continued re-qualification.
Summary
In any VHP/vH₂O₂ cycle development, VHP-PQ and re-qualification studies, it is necessary to manage variations in the quality or efficacy resistance of biological indicators. BI pre-use qualification studies are recommended to be applied to assess BI quality and efficacy variations as a quality control check before using BIs in any efficacy qualification studies in a GMP manufacturing production setting. Pre-use BI qualification reduces the impact on subsequent cycle efficacy studies and improves the efficiencies and qualification times.
For BIs that have completed pre-use qualification studies (Enumeration, System D Value, SEMs and Rogue Incidence rate studies) and are subsequently used in cycle efficacy challenge studies, it is necessary to manage the potential and inherent risk of unexpected BI positives due to ‘Rogue BIs’.
Two strategies are considered: applying BI challenges as duplicate (strategy 1) or triplicate (strategy 2) BIs at each efficacy challenge location and guidance is provided on managing unexpected BI positives within development and qualification cycles.
The incidence rate of BI Rogue has varied over the years and continues to vary due to BI quality deviations from BI manufacturers as a result of difficulties to consistently manufacture such biological systems, so consistency cannot be assumed or expected. Quality control checks are paramount for monitoring BI quality and managing Rogue BIs in qualification cycles. Decisions not to use a BI lot because of quality deviations and potential impact on qualification studies must be supported by independent QC study data.
Provided Biological indicator 6log reduction and Enzymatic indicator RLU can be correlated for a GMP manufacturing production setting, EIs can support increased understanding of log reduction efficacy at challenge locations, but, more importantly, they can also be used to support evidence that an unexpected BI positive was a Rogue BI.
BIs are still considered the primary cycle qualification challenge and EI only data is not accepted. In any account BI and EI correlation is required before EI data (RLU) can be interpreted with log reduction and the fundamental measure of biological efficacy. Following correlation studies and qualification with BIs and EIs it may be possible to consider EI only data in ongoing re-qualification studies but such a strategy would be subject to study data and regulatory approval at the time.
VHP/vH₂O₂ efficacy qualification strategies, including the management of BI quality issues and Rogue BIs, should be defined, justified and documented references included as part of the contamination control strategy (CCS). BIs remain the primary focus of VHP/vH₂O₂ cycle qualification studies, with EIs being used as supportive technology (not as a replacement for BIs). The benefits of using EIs are considered an improvement to the characterisation of cycle efficacy that will be of benefit all future VHP/vH₂O₂ qualification studies.
PHSS; Pharmaceutical Healthcare Sciences Society: Biological Indicator SME focus group:
James L Drinkwater: Franz Ziel GmbH (partner with Koerber) Head of GMP compliance and Ex-Chairman and honorary member of the PHSS: Pharmaceutical and Healthcare Sciences Society. Member of PDA TR51 Biological indicator manufacture guidance working group. Member of PDA UK Chapter board of directors.
Dr Graham Steele; Founder Microserve. PHSS Editor-in-Chief for European Journal of Parenteral and Pharmaceutical sciences. Member of the PDA TR51 Biological indicator manufacture guidance working group.
Dr. Birte Scharf: Senior Scientist GMP Compliance Franz Ziel GmbH (partner with Koerber). Member of PHSS aseptic processing and Biocontamination special interest group.
References
Drinkwater J, Chewins J and Steele G (2009) Biological indicators don’t lie, but in sporicidal gassing disinfection cycles do they sometimes confuse the truth? European Journal of Parenteral & Pharmaceutical Sciences, vol. 14, no. 1, pp. 5-10, 2009.
Eddington D (2016) Heads or Tails – Statistical Methods for Interpreting Multiple Biological Indicator Results. PDA Letter, September, pp. 22-27, 2016.
European Commission (2022) EudraLex Volume 4: EU Guidelines for Good Manufacturing Practice for Medicinal Products for Human and Veterinary Use – Annex 1: Manufacture of Sterile Medicinal Products.
European Commission (2022) EudraLex Volume 4: EU Guidelines for Good Manufacturing Practice for Medicinal Products for Human and Veterinary Use – Annex 1: Manufacture of Sterile Medicinal Products.
Schachtschneider A, Klein S and Marshall K (2022) Application of Enzyme Indicators in Hydrogen Peroxide Biodecontamination Cycle Development A Critical Evaluation of Indicator Variability and Correlation to Biological Indicator Results. PDA Journal of Pharmaceutical Science and Technology, no. 76, pp. 34-51, 2022.
Scharf B and Kranenburg H (2022) Enzymatische Indikatoren in H2O2-Bio-Dekontaminationszyklen Teil 1. TechnoPharm, vol. 12, no. 2, pp. 84-90, 2022.
T. El. Zarif, M. Yibirin, D. De. Oliveira-gomes, M. Machaalani, R. Nawfal, G. Bittar, H.F. Bahmad, N.Bitar. Overcoming Therapy Resistance in Colon Cancer by Drug Repurposing, Cancers 14(9) (2022) 2105.
Authors
James Drinkwater
Franz Ziel GmbH / PHSS
PHSS SME BI Quality focus group
Contributing Authors: Birte Scharf - Franz Ziel GmbH, Graham Steele - PHSS/ EJPPS Editor-in-Chief
* Corresponding author:
James Drinkwater jamesdrinkwater@phss.co.uk