Investigations on the efficacy of surface disinfection and surface cleaning procedures. 2. Laboratory testing of the efficacy under conditions simulating those of real-life.

Using a standardised method (impression method by means of 'Rodac' plates and glass as well as ceramic surfaces as germ carriers) we tested for the efficacy of 3 surface disinfectants (aldehydes, aldehydes + detergent substances, phenol derivatives) and 3 disinfectant cleaning agents (aldehydes + detergent substances + wax) and 2 per cent soft soap solution on Staphylococcus aureus, Klebsiella pneumoniae and Sarcina lutea. The method enabled us to calculate the actual germ count reduction and also took account of the natural dying-rate of the test organisms. Their resistance to the different types of active substances varied greatly. Thus the 3 disinfectants had a better effect on Klebsiellae and Staphylococci than on Sarcinae. 2 of the 3 disinfectant cleaning agents, on the other hand, turned out to be less suitable for the elimination of Klebsiellae. It thus follows that Sarcina cannot be used as test organism for in-use tests (see Communication 1) unless the resistance of Staphylococci and Klebsiellae to the test preparation has first been established in laboratory experiments. The general question, namely whether in-use tests provide meaningful and accurate results remain to be elucidated. On the basis of our test results, the exclusive use of soap for cleaning floors, as a substitute of disinfection, should definitely be ruled out. Although soap reduces Gram-positive cocci well in actual practice, it is almost ineffective against problem germs such as Klebsiellae. What should be stipulated is the use of broad-spectrum disinfectants, i.e. they should, if possible, act equally well against different types of germs. From the commercially-available preparations that were tested, a phenol-base product gave the best results. On the basis of these results we venture to doubt that the use of aldehyde preparations which is customary at the moment, is the right approach to fight hospital infections.