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The situation of hospital hygiene in Belgium and in the Netherlands is described in the light of the official regulations, the composition and the functioning of the infection committee and of the hospital hygiene team, and the availability of official or semi-official guidelines. Typical for the Netherlands in the long tradition of issuing guidelines on hospital hygiene, in the beginning in 1966 in the form of an advice of the Health Council, at present in the guidelines of the Working Group on Infection Prevention (WIP). A particularity for Belgium is the financing by the state of the hospital hygiene doctor and the hospital hygiene nurses based on a system of scores in which the beds of specialisms with a higher infection risk count for more than general beds.

Four methods for the evaluation of the bactericidal property of disinfectants have been compared. These methods are (1) the qualitative suspension test of the directives for the testing of disinfectants of the German Society for Hygiene and Microbiology, (2) the quantitative suspension test of the dutch committee on phytopharmacy, (3) the carrier or use-dilution method of the A.O.A.C. and (4) the KELSEY and SYKES' capacity test. Aim of this study has been the evaluation of (1) the repeatability and reproducibility of the test results of the four methods, and of (2) the agreement of the degree of efficiency as determined by the different techniques. At least three dilutions of the three disinfectant standards (a phenolic, an aldehyde solution and an iodophore) have been tested against Staphylococcus aureus and Pseudomonas aeruginoas. In this article the authors describe the methods used and the specific difficulties of these techniques. In the suspension technique of the DGHM, the use of only one subculture is stated as not sufficient for exact evaluation of the extinction. In the dutch suspension test, the use of pour plates leads to troubles. The preparative incubation time of the use-dilution method of the A.O.A.C. has been experienced as too long. The structure of the KELSEY and SYKES' test is complicated. Also the results by the two research-teams, are reported and summarized. It has been found that the transition from active to inactive dilution is most marked in the two suspension tests, whereas the distinction between the results of the use-dilution method of the A.O.A.C. is not so clear.

At present the testing and assessment of disinfectants is carried out according to different methods in different countries. The result of this is that certain preparations or concentrations are allowed for use in some countries while they are not in neighbouring countries. A study was carried out jointly at two universities with the object of testing the reproducibility of these methods and standardizing them. Furthermore, an attempt was to be made to arrive at common test methods. In 2 labortories (A,B) we tested and compared the disinfectant activity of three disinfectant standards (phenol, aldehyde, iodophor) against Staphylococcus aureus and Pseudomonas aeruginosa (1) in the suspension test according to the "Richtlinien für die Prüfung chemischer Desinfektionsmittel" (Directions governing the testing of chemical disinfectants) of the DGHM, (2) in the suspension test of the "Dutch Commission for Phytopharmacy," (3) according to the "Use-Dilution Method" of the A.O.A.C. and (4) in the capacity test according to KELSEY and SYKES. Every individual test was repeated ten times. In addition we determined the reproducibility of the results by repeating the tests several times with one and the same culture and with different cultures (on different days). The exact method is described elsewhere (7). The statistical evaluation of the mean values (Tables 1,3,5 and 7) and variances (Tables 2,4,6 and 8) leads to the following findings: The results obtained with the various methods depend on the lab. technique and were specific to the germs and preparations tested. The reproducibility was best in the DGHM suspension test and the capacity test according to KELSEY and SYKES; the mean values of the two laboratories were closest for the Dutch test of the Commission of Phytopharmacy. The greatest mean value differences and scatter were observed with the A.O.A.C. "Use-Dilution Method." The conclusion of this investigation is that for the preliminary testing of disinfectants a method should be recommended which enables the determination of the acturl germ count reduction after varying periods of action and with well-defined organic challenge. In order to assess the disinfectant action, however, such a test - which answers most of our questions and has optimum reproducibility - must be supplemented by main tests which simulate practical conditions as near as possible.

The bactericidal activity of three disinfectant standards has been determined by four national methods (the qualitative suspension test of the German Society for Hygiene and Microbiology DGHM, the quantitative suspension test of the Dutch Committee on Phytopharmacy, the use-dilution method of the A.O.A.C. and the Kelsey and Sykes' test) in order to compare these four testing techniques. In previous publications the results of these experiments and the degree of standardisation of the four methods have been tested. The purpose of the present study is to evaluate to what extent the results obtained by the four testing techniques do correspond. The bactericidal activity can be expressed as a germicidal effect. In theory (Tab. 1) the values of germicidal effect can be similar for the four testing techniques. In practice (Tab. 2 and 3) it has been found that with the suspension technique of the DGHM systematically higher values are obtained than in the other tests. These can not be compared to each other, because the medication times differ. Although the values of the germicidal effect obtained are widely different, it can happen that the minimum effective concentration determined by the four methods be identical as each of these methods applies different criteria. The authors have therefore calculated the minimum effective concentration which is required for the disinfectant standard by the four disinfectant testing techniques (Tab. 4). Even here, no correspondence has been found between the four methods. The lethal concentration of the disinfectant standards determined by the use-dilution method of the A.O.A.C. is thus 2 to 16 times those required by the Dutch suspension test. The difference in effective concentrations, however, is not constant and is not related to the type of disinfectant or the test organism. In consequence, there is no way of establishing a comparison between the results of the four methods with a view to setting up a conversion table. Each disinfectant testing technique has its own characteristics.