THE TESTING OF DISINFECTANTS

Although all disinfectant tests have the same final purpose, namely me asuring the antimicrobial activity of a chemical substance or preparat ion, a large number of testing methods has been described. They are su bdivided into suspension tests, carrier and surface disinfection tests and other practice-mimicking tests. The suspension tests comprise qua litative and quantitative suspension tests, and, as derived tests, the determination of the phenol coefficient and capacity tests. There is an essential difference between a carrier test and a surface disinfect ant test: in the former case the carrier is submerged in the disinfect ant solution during the whole exposure time, whereas in the latter cas e the disinfectant is applied on the carrier for the application time and thereafter the carrier is drying during the exposure. The basic pr inciple now widely accepted is that the antimicrobial efficiency of a disinfectant is examined at three stages of testing. The first stage c oncerns laboratory tests in which it is verified whether a chemical co mpound or a preparation possesses antimicrobial activity. For these pr eliminary screening tests, suspension tests are considered. In the sec ond stage of tests, disinfection procedures and not disinfectants are examined. It is determined under which conditions and at which use-dil ution for a given application the preparation is active: the tests sim ulate real-life situations; such tests are carrier tests for the disin fection of materials by submersion and surface disinfection tests. The last stage takes place in the field, and comprises the in-loco or in- situ tests with as variants the in-use tests, which examine whether, a fter a normal period of use, germs are still killed by the disinfectan t solution. It is the task of the European and international standardi zation organisations to develop new standards and to elaborate tests, which predict the effectiveness of a preparation in practice under var iable circumstances. (C) 1998 Elsevier Science Ltd. All rights reserve d.