Effect of AHP Disinfectants on Cage Integrity

Background & Purpose

Effective sterilization of animal caging is required prior to their removal from high-containment facilities to ensure biosafety. However, repeated sterilization events can lead to cage cloudiness and loss of integrity. Maintaining good visibility of plastic cages is critical for performing health checks and ensuring the welfare of laboratory rodents.

Previous application of disinfectants can exacerbate the negative effects of sterilization on cage integrity, and removal of disinfectants from cages prior to autoclaving is preferred to slow or prevent these effects. However, washing rodent caging prior to autoclaving in high-containment facilities is not often feasible — and so selecting disinfectants that effectively inactivate experimental pathogens but have minimal effects on cage transparency and integrity is needed.

Texas Biomed experienced many cages becoming opaque so that observations could no longer be done cage-side at an accelerated rate. The purpose of this experiment was to confirm the cause of loss in transparency. The original hypothesis was that corrosive disinfectants — specifically phenolic solutions — would lead to impaired transparency at a faster rate than other non-corrosive disinfectants.

Methods

New cages were ordered and separated into four groups. Each group was then sprayed with one of three disinfectants — 1) a phenolic disinfectant, 2) a peroxide-and-surfactant-based disinfectant, or 3) an alcohol-based disinfectant — or were left untouched as a control. The disinfectants were allowed to fully dry, and the cages were autoclaved using standard sterilization settings of 121°C for 30 minutes.

The cages were allowed to cool completely, at which time the disinfectants were reapplied and the autoclave cycle repeated. The autoclaving and disinfectant reapplication process was repeated ten times for each group to simulate the cumulative effects of repeated sterilization cycles on the cage material, mimicking real-world conditions in high-containment facilities over time.

Results

No significant change in transparency was observed in any group after repeated cycles. The Wex-Cide group had very little change of any kind. However, the three cages sprayed with Peroxigard — an accelerated hydrogen peroxide (AHP) disinfectant — before autoclaving experienced significant cracking after just three cycles and were determined to be unusable after six cycles. Discovering how detrimental Peroxigard is to the integrity of polysulfone plastic was a significant finding of this study.

All other cages — sprayed with Wex-Cide, 70% ethanol, or left as untreated controls — had no significant change in visibility or structural integrity after 10 cycles.

Conclusions

The study clearly demonstrates that the transparency of polysulfone cages remains largely unaffected by repeated sterilization cycles when using phenolic or alcohol-based disinfectants, or no disinfectant at all. The observation of etching after just one autoclave cycle with the peroxide-and-surfactant-based disinfectant raises critical concerns about its long-term use in environments where repeated sterilization is necessary.

Facilities should prioritize the selection of disinfectants that have been demonstrated to maintain cage quality over repeated use. Phenolic disinfectants and 70% ethanol appear to be significantly safer alternatives for maintaining cage integrity in high-containment settings.

Considerations & Future Research

The researchers believe that their inability to fully replicate the conditions of the cages in high containment may stem from not accounting for the repeated exposure to disinfectants that occurs when staff and researchers open the cages. In future studies, they aim to extend the experiment by applying the disinfectants multiple times over an extended period before autoclaving — more accurately reflecting staff interactions with the cages.

Additionally, it would be valuable to investigate how the peroxide-and-surfactant-based disinfectant impacts cages under these updated conditions. The team also plans to explore alternative disinfectants to identify a more broadly suitable option, and to assess whether adjustments to lab practices could help prevent cloudiness and cracking in polysulfone cages.

Acknowledgements

The research team extends their heartfelt thanks to Tecniplast for supplying the new cages utilized in this study, and to the vivarium staff, lab technicians, and all volunteers whose time and effort made this research possible.

Institutions:
¹ Integrated Research and Technology Core, Texas Biomedical Research Institute, San Antonio, TX
² University of North Carolina at Chapel Hill, Chapel Hill, NC
³ Texas Biomedical Research Institute, San Antonio, TX