Influence of biofilms by chemical disinfectants and mechanical cleaning.

Water conducting systems in hospitals (endoscopes, nebulizers, tap water systems, dental units etc.) are often important reservoirs of conditional pathogens. The sanitation of those systems by in vitro efficient chemical disinfectants is very difficult. An explanation may be that microorganisms are growing in such systems in wall adhering biofilms wherein they are protected from biocides. A method for testing the efficacy of chemical disinfectants and mechanical cleaning is described under conditions which imitate those in natural systems. A criterion for the efficacy of sanitation procedure is not only the good disinfection result but also the removal of biofilms. The investigation showed that aldehydes, and peracetic acid can reduce multiplying microorganisms without disrupting the biofilm. A preparation on the basis of hydrogen peroxide showed good antimicrobial efficacy and a distinct reduction and influence of the biofilm. The best result was achieved by mechanical cleaning. The test model is simple and a supplement to the conventional in vitro laboratory test for the efficacy of sanitation procedures of water conducting systems.