Evaluation of a flash disinfection process for surface decontamination of gamma-irradiated feed packaging

Ensuring biosecurity for pathogen-free rodents generally requires processing all materials that come in direct contact with the animals, including feed, to reduce or eliminate unwanted adventitious agents. A common method of processing animal feed is gamma irradiation. Irradiation is performed offsite and requires transport of feed from the irradiator to the point of use, potentially resulting in surface contamination of the packaging. We tested whether an autoclave could be used to provide a flash disinfection cycle to decontaminate the outer feed packaging while having a limited effect on nutritional feed quality. We developed a standardized and repeatable method, which involved attaching sterile glass vials containing Pseudomonas aeruginosa- and Staphylococcus aureus-laden culture broth onto the bag's surface, to validate effectiveness of the process. Nutritional analyses verified that the flash process had minimal effect on feed quality. Gas chromatography-mass spectrometry confirmed that subjecting feed packaging to the elevated cycle temperatures and pressures did not result in feed contamination by the packaging materials. The lowest autoclave setting that produced consistent surface disinfection, as determined by 3 consecutive negative cultures, was exposure of the bag surface to a chamber temperature of at least 82 degrees C for a minimum of 2 min. This flash disinfection process has been implemented successfully in 5 vivaria supporting more than 35,000 rodent cages daily.