Validation of an Autoclave Procedure for Sterilization of Mouse (Mus musculus) Carcasses

Autoclaving as a Routine Method for the Decontamination of Animal Carcasses in a Biosafety Level 3 Facility

Introduction

Carcasses from animal experiments with RG-3 pathogens should be decontaminated onsite in Austria.

Objective

The aim of this study was to find out if the use of pass-through autoclaves for the decontamination of animal carcasses (up to 40 kg of weight) could serve as a routine method for smaller laboratories, as the installation of special carcass decontamination plants may be cost prohibitive.

Methods

Biological indicators (BIs) were implanted into the carcasses of animals of different sizes and species with a novel method using stainless steel pipes. The bodies were placed in autoclavable plastic bags and equipped with thermal probes by insertion through the rectum. Subsequently a factory default autoclave cycle for liquids was performed, which holds a core temperature of 121°C for 20 min.

Results

The weight of the carcasses ranged from 1 to 42 kg, the duration of the individual cycles reached from 2.2 to 17.23 h. Decontamination was successful every single time as shown by the BIs. The application through the natural orifices with the help of the application tools seems to offer a reliable alternative for implanting the BIs into the carcasses without creating new openings. Insulation properties did not pose substantial challenges to the process. Limitations on the packaging procedure were identified in carcasses larger than 30 kg.

Conclusion

Based on the results of this study, using pass-through autoclaves represents an option as a routine method for the decontamination of animal carcasses up to at least 40 kg.

Thermal Inactivation of Carcasses of Mice and Rabbits Infected with Pathogens of Risk Groups Two to Four

Pathogenesis of viruses or other agents that are infectious to humans is frequently studied in vivo using natural or genetically modified animals. Depending on the risk group of the pathogen, the majority of such experimental studies are performed at least under biosafety level 2 (BSL-2) conditions. Biosafety considerations are therefore critical at all steps of research involving potentially infectious pathogens. Inactivation of pathogens studied using in vitro experiments is usually performed using moist heat sterilization. However, few standardized and validated protocols are currently available for the thermal inactivation of carcasses from laboratory animals infected with such human pathogens. To comply with laboratory biologic safety rules and requirements imposed by regulatory authorities, documentation of appropriate inactivation conditions or use of a validated procedure according to national or international standards is critical. In the current study, we evaluated inactivation protocols in a standard laboratory autoclave for carcasses of either frozen mice or recently terminated rabbits, which were placed inside autoclave bags with bedding material in stainless steel containers. Temperature sensors were placed into different tissues of the carcasses to continuously record temperature in situ and in real-time, and a reference sensor was placed in the autoclave. To achieve pathogen inactivation, autoclaving protocols had to be optimized for both species. Frozen mice required 2 different fractionated prevacuum stages, whereas recently terminated rabbits required 3 different fractionated prevacuum stages. This study provides a template for an evaluation procedure to safely and effectively inactivate mice and rabbits infected with risk group 2 to 4 pathogens.