Limited efficacy of steam sterilization to inactivate vCJD infectivity

The transmission of bovine spongiform encephalopathy (BSE) to humans as variant Creutzfeldt-Jakob Disease (vCJD) raised concerns about potential secondary transmissions due to the resistance of the agents causing transmissible spongiform encephalopathies (TSEs), sometimes known as prions, to commonly used methods of sterilization, notably steam sterilization (or autoclaving). It has been suggested that surgical instruments and other medical devices might retain sufficient infected tissue debris after cleaning and steam sterilization to infect patients on whom they are subsequently used.

To determine whether concerns about the lack of efficacy of steam sterilization of vCJD were justified.

The reduction in infectivity of brain macerates of vCJD brain after steam sterilization using the standard temperatures and time recommended for autoclaving in UK hospitals (134-137°C for 3 min) was measured.

Reductions in titre of 10(2.3) to >10(3.6) ID(50) were found. In three of four samples, infectivity was recovered after steam sterilization.

As noted previously, TSE strains derived from BSE sources appear to be more resistant to steam sterilization and other forms of heat inactivation than other TSE sources.