Differences in adhesion and biofilm formation of several clinical isolates of Staphylococcus epidermidis

Staphylococcus epidermidis and similar coagulase-negative staphylococci (CoNS) are now well established as major nosocomial pathogens associated with infections of indwelling medical devices. The major virulence factor of these organisms is mainly due to their ability to adhere to devices and form a biofilm.however, it is not known if adherence and biofilm formation are closely linked phenotypes for clinical isolates. since different clinical isolates of s. epidermidis would be expected to exhibit different phenotypic behaviours it is further expected that strains of s. epidermidis might have different abilities to adhere to synthetic surfaces and subsequently produce biofilms. in this study the initial adherence and subsequent biofilm formation properties of 9 clinical isolates of s. epidermidis along with biofilm+ and biofilm– control strains were assayed. the adherence results were interpreted in terms of the physico-chemical interaction established between the cells and the adhesion substratum as assessed by contact angle measurements.as expected, the clinical isolates exhibited different abilities to adhere to hydrophilic glass and to form biofilms. moreover, the strains that produced the highest amounts of biofilms were not the ones able to adhere to the largest extent and vice-versa. for example, the biofilm- control strain actually showed the highest level of initial adhesion capability and did not produce biofilm. these results indicate that high levels of initial adherence do not necessarily lead to strong biofilm formation and that some strains do not have a high initial adherence but can subsequently form a strong biofilm. these two aspects of the pathogenesis of medical device related-infection may need to be evaluated independently to ascertain the contribution of each to the virulence of cons causing device related infections