BACTERIAL ADHESION TO MEDICAL MATERIALS - CLEANSING EFFICACY

A means of bacterial survival: Adhesion is a universal phenomenon obse rved on cellular or artificial surfaces and is the prelude to coloniza tion, and in man to infection. Three successive phases: Adhesion occur s rapidly and although reversible in the first phase quickly becomes i rreversible as bacteria accumulate and produce exopolysaccharides or s lime which guarantee their survival by protecting them from antibiotic s or disinfectants. Surfaces: The nature of the adhering germs varies with the type of surface. Staphylococcus strains predominant on dry su rfaces and Pseudomonas on wet surfaces. Adapted tests: The adhesion pr operties of germs must be taken into account when cleansing the surfac es of medical equipment as well as materials used in the food and cosm etic industries. Microbiological criteria based on culture of microorg anisms 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 co untries. In vitro evaluation: The European standard established in 199 3 defines the technical conditions for testing for bacteria on surface s. These techniques are used to test automatic or manual cleansing pro cedures and have shown that bactericidal concentrations for surfaces a re higher than those obtained with the standards usually applied for b acterial suspensions. Standardisation is required to establish precise cleansing criteria for optimum disinfection using products adapted to microorganisms and their metabolism (choice of products, their concen trations and duration of exposure). (C) 1997, Masson, Paris.