Bacterial adhesion to medical materials: Cleansing efficacy

A means of bacterial survival: Adhesion is a universal phenomenon observed on cellular or artificial surfaces and is the prelude to colonization, and in man to infection. Three successive phases: Adhesion occurs rapidly and although reversible in the first phase quickly becomes irreversible as bacteria accumulate and produce exopolysaccharides or slime which guarantee their survival by protecting them from antibiotics or disinfectants. Surfaces: The nature of the adhering germs varies with the type of surface. Staphylococcus strains predominant on dry surfaces and Pseudomonas on wet surfaces. Adapted tests: The adhesion properties of germs must be taken into account when cleansing the surfaces of medical equipment as well as materials used in the food and cosmetic industries. Microbiological criteria based on culture of microorganisms suspended in liquid media is insufficient to test the activity of disinfectants on surfaces. Microorganisms adhering to a surface or present in the biofilm covering the surface have increased resistance against antibiotics and disinfectants. Tests to evaluate the effect of these agents on adherent bacteria have been developed in different countries. In vitro evaluation: The European standard established in 1993 defines the technical conditions for testing for bacteria on surfaces. These techniques are used to test automatic or manual cleansing procedures and have shown that bactericidal concentrations for surfaces are higher than those obtained with the standards usually applied for bacterial suspensions. Standardisation is required to establish precise cleansing criteria for optimum disinfection using products adapted to microorganisms and their metabolism (choice of products, their concentrations and duration of exposure). (C) 1997, Masson, Paris.