QUANTITATION OF BACTERIAL ADHESION TO POLYMER SURFACES BY BIOLUMINESCENCE

Quantitation of microbes adhering to a surface is commonly used in stu dies of microbial adhesion to different surfaces. We have quantified d ifferent staphylococcal strains adhering to polymer surfaces by measur ing bacterial ATP (adenosine triphosphate) by bioluminescence. The met hod is sensitive, having a detection limit of 10(4) bacterial cells. V iable counting of bacterial cells may yield falsely low results due to the presence of ''dormant'' and adherent bacteria. By using biolumine scence, this can be avoided. Cells of different bacterial species and cells of strains of the same species were shown to differ significantl y in their basal ATP content (8.7 x 10(-13) - 5.2 x 10(-22) MATP). The size of adherent and planktonic bacteria decreased with time (0.7 mu m --> 0.3 mu m, 20 days). During incubation in nutrient-poor buffer (' 'starvation''), the ATP content of adherent bacteria decreased after 2 4-96 h whereas that of planktonic bacteria was stable over 20 days. Th e presence of human serum or plasma did not interfere significantly wi th the test results. Since the ATP concentration of bacterial strains of different species varies and is also influenced by the growth condi tions of bacteria (solid or liquid culture medium), a species-specific standard curve has to be established for bacteria grown under the sam e culture conditions. We conclude that the method is a sensitive tool to quantify adherent bacteria during experiments lasting for less than 6 h and constitutes a valuable method to be used in conjunction with different microscopical techniques.