Dear Sir,

What should be the disinfection temperature and time during the final rinse in a standard washer disinfector as per the european standards?

Thanks and regards,
NORBERTO.

Norberto

The European Standard will not state set time/temperature relationship for thermal disinfection. It will, however, say that disinfection will be acceptable if the Ao value is 600 for surgical instruments. The Ao concept has been defined in the Standard as an equivalent thermal input to 1 second at 80 C. Thus, the Standard will be met if there is an exposure of all instruments to 80 C for 600 seconds, or 10 minutes. However, it will also allow for disinfection at any temperature above 65 C as long as the thermal input is equivalnet to 10 minutes at 80 C. Acceptable values could therefore include 1 minute at 90 C or 100 minutes at 70 C. It could also include disinfection at a varying temperature (above 65 C) if the Ao value is met. This will require a control system with temperature sensor(s) providing constant data that the control system can integrate and compare with the lethality at 80 C. It can then advance the cycle to drying once the Ao value has been met.

We in the UK are currently working to time/temperature relationships that will not meet the Ao of 600 so we will have to increase the exposure times to suit once the Standard is published.

I hope this explains the concept within the forthcoming EN ISO 15883.

Peter Hooper, UK

Dear,

In "Practical guide to validation of cleaning and disinfection processes" mhp-verlag, you can find he following additional comment on the Ao value.

"Which Ao value has to be reached depends on the type and number of microrganisms on the contaminated medical device as well as on any subsequent treatment or final rinse.
This must be agreed with the responsible hospitalinfection control specialist. The application of an Ao value of 600 is viewed as a minimum standard for non-critical medical devices, i.e. those devices that only come into contact with the intact skin. A further precondition is that there should be only slight microbial contamination and no heat-resistant pathogens. An Ao value of 600 can be reached at 80°C for 10 min, 90°C for 1 min or at 70°C for 100 min.
In the case of medical devices contaminated with heat-resistant viruses, e.g. hepatitis B virus, an Ao value of at least 3000 is required. This can be achieved by exposure to hot water, e.g. at 90°C, provided that the medical device can tolerate this temperature for at least 5 min. The Robert Koch institute recommends thermal disinfection with an Ao value of at least 3000 for all critical medical devices, corresponding to the A and B spectrum of action. This Ao value must be observed if the presence of pathogens with a higher heat resistance profile can be assumed."

Best regards,
Wim Renders