[Scanning electron microscope demonstration of wall colonization of water-bearing plastic tubes]

A polyethylene and a silicone tube from water leading system of a dental unit, in which Pseudomonas aeruginosa could be isolated, were investigated by S.E.M. (Scanning Electron Microscopy). In the tubes thick deposits of extracellular material were found, in which microorganisms were embedded or on which they were free-lying. Pretreatment of the water systems by irrigating and by disinfection was unsuccessful. The possible protection of microorganisms by the demonstrated extracellular material against hydraulic forces and disinfection is discussed.