Milestones in the testing of surface disinfectants: from Robert Koch to CEN TC 216

The first publication on testing disinfection procedures dates back to 1881 and was compiled by Robert Koch. Although his conclusions were erroneous, we continue to use the “germ carrier test” right up to the present day even if preference is now given to the suspension test first devised by Geppert. Over the years many conceptual milestones had to be reached, and much knowledge and many insights were needed to develop this procedure further to ensure reproducible results. Today, the disinfectant effect is calculated in terms of logarithmic reduction factors for the microbial count: a reduction of 5 log levels has been agreed, i.e. an inactivation kinetics of 99.999%. Of paramount importance was, in particular, the insight that different methods had to be employed to test disinfectants, while doing so not only in the laboratory but also under everyday working conditions. This gave rise to a situation whereby each country developed its own test methods, producing significantly different results. It was only in 1970 that the parties concerned came together so as to reach a uniform solution in Europe. The achievements of the “International Colloquium” were later adopted and continued by the European Standardization Committee (CEN) in a special working group (TS 216). The most important accomplishment of this working group is, no doubt, the insight that it is not a test result but rather a test system that will reveal the truth. The tests carried out in Phase 1 are quantitative suspension tests to elucidate the bactericidal, virucidal, tuberculocidal, fungicidal and sporicidal efficacy. Phase 2 defines the requisite concentration per exposure time. CEN was founded and is sponsored by industry, since the latter needs reliable standards. Time will tell whether this was not perhaps the greatest milestone in the development of test methods. However, the successes scored by CEN are ultimately only the logical consequence of the accomplishments already achieved by the “International Colloquium”. In reality, most of the procedures that today have been accepted via TS 216 are based on the activities set in motion by the Colloquium. It is impossible to acknowledge just how pivotal was the role played by both legendary “International Colloquia” in 1970 and 1972 in Hamburg in the development of uniform test procedures.