Investigations on the efficacy of surface disinfection and surface cleaning procedures. 1. Tests under real-life conditions.

The suitability of disinfection preparations is assessed on the basis of laboratory tests, different methods being used in the various countries. Since such model tests are rather inadequate when it comes to judging surface disinfectants, additional in-use tests are desirable. They might, in any case, serve as a reference system for judging the evaluation criteria which still differ widely at the moment. The experiments described in this study were chiefly designed to establish the effect of cleaning and disinfection measures on bacteria normally present on surfaces and on the artificial contamination of surfaces with Sarcinae as model germs. The tests were carried out in the halls on 5 floors of a medical (lift landings). "Rodac" plates were used to identify the germs. 3 disinfectants (aldehydes, phenol derivative), 3 disinfectant cleaning agents and soft soap were used. The preparations reduced the normal germ count by approx. 80 per cent. The reduction was mainly due to the cleaning effect (soft soap was as effective as the preparations with disinfectant properties). The effect on the "normal germ count" cannot, therefore, be used as sole criterion of disinfectant action. When the various preparations were applied in twice the concentration recommended for Staphylococcus hospitalism, the Sarcina count was reduced by 99 to 99.9 per cent within 2 hours. The efficacy of disinfectants and disinfectant cleaning agents was practically the same. Additional laboratory tests are necessary before the effect of soft soap can be finally assessed. In actual practice the unit count of pathogenic germs- such as Staphylococci and Klebsiellae- is too low to enable an objective assessment of a disinfectant to be made. On the other hand, artificial contamination with such pathogens is not possible because of the risk involved. The use of Sarcina lutea as test germ is therefore subjects to certain limitations. One of the prerequisites for using it is, for example, prior reduction of the normal germ count to values of less than 500/100 cm2. The second communication will report on investigations into the chemoresistance of Sarcina and how this compares with that of Staphylococcus aureus and Klebsiella. The need for such studies arose from our present investigation.