Investigations on the efficacy of surface disinfection and surface cleaning procedures. 3. Evaluation of the results of in-use and laboratory tests.

3 disinfectants and 3 disinfectant cleaning agents were subjected to comparative tests as to their germicidal activity. These were (a) laboratory tests with germ carriers and (b) in-use tests with Sarcina-contaminated floor surfaces in a medical institute. The results, details of which are given in the two preceding publications, were assessed under the following angles: Validity of the test methods, requisite changes of the test procedures and practical usefulness of the different types of preparations. This assessment led to the following conclusions: New preparations should first be tested for their bacteriostatic activity according to DGHM and the neutralising agents should be determined. The suspensions tests - which remain to be standardised- provide information on the sensitivity to protein, hard water and detergent surface active substances. The germ carrier tests with operating-theatre tiles, carried out with at least 5 test germs, must result in a germ count reduction of more than 5 powers of ten (regardless of the elimination rate due to drying). In-use tests should stand at the end of the test series. Regular epidemiological studies are hardly feasible in all individual cases. An assessment on the basis of the behaviour of normal bacterial spores is likewise impracticable. The use of test germs cannot be dispensed with. Sarcina is a suitable species provided germ-carrier tests have first been carried out and have shown that Staphylococci, Klebsiellae and other high-risk germs are more sensitive to the preparation than Sarcina lutea. In the in-use tests, we consider a reduction by 2 to 3 powers of ten to be sufficient.