Thoughts on levels of microbial cleanliness and on validating disinfection procedures

Efforts of the European Committee of Standardization (CEN) and the International Organization for Standardization (ISO) to harmonize production standards for medical devices have brought to the fore the need to standardize definitions and names for different levels of microbial contamination as well as validation procedures for microbial inactivation. Spaulding's categories of medical devices (critical, semi-critical and noncritical items) suggest that different levels of cleanliness can be accepted. Current terminology is imprecise and does not provide the necessary information to the user. A more appropriate one is needed. So are methods to validate microbial inactivation processes to lower levels of cleanliness than sterility. In Sweden, a couple of validation studies have been performed on bacterial inactivation in automatic washing machines which disinfect through a final hot water or steam rinse. However, more studies need to be done, especially on viral inactivation.