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
