Simplified Method to Test Decontamination of Bovine Spongiform Encephalopathy Agent Dried on Steel Surfaces.

BACKGROUND

Transmissible spongiform encephalopathy (TSE) agents are lethal unconventional pathogens that have infected both humans and animals. Bovine spongiform encephalopathy (BSE) is a TSE. TSE agents are unusually resistant to inactivation. In-use tests conducted to investigate those products involve intentionally contaminating carrier objects with TSE agents, exposing them to decontaminating regimens, and then surgically implanting treated carriers into TSE-susceptible rodents to assay for TSE infectivity.

OBJECTIVE

To adapt a simple in-use carrier test to decontaminate TSE agents based on methods employed for decades to test for bacteria, fungi and viruses remaining on surfaces treated with disinfectants, known as "use-dilution tests."

METHODS

We serially diluted 10% BSE brain homogenate in a normal bovine-brain-tissue paste and contaminated 60 stainless-steel pins mounted in disposable heat-resistant plastic holders with the lowest dilution and five or six pins with each successive dilution. We investigated 2N NaOH-known to inactivate TSE agents-with and without autoclaving (121 °C and 134 °C) and autoclaving without exposure to NaOH. Each pin was briefly introduced into the brain of an anesthetized mouse. We monitored animals for 24 months. At the end of the study, the brains of all mice (except six mice that died early post inoculation) were tested for the presence of abnormal prion protein, a marker of TSE infections. Next, we calculated the level of inactivation provided by each method.

RESULTS

Our results indicated that none of the 60 animals inoculated with pins decontaminated with NaOH (with or without autoclaving) developed BSE while steam autoclaving alone at both conventional and elevated temperatures was not effective. This inactivation corresponded to ≥ 1.1 log10 reduction of infectivity.

CONCLUSION

Using our relatively simple and quick pin method with brief intracerebral punctures without surgical implantation, we tested many more replicate treated carriers than in studies previously reported while yielding similar results.

HIGHLIGHTS: The proposed pin method was proven effective to evaluate inactivation regimens for BSE agents.