Quantitative analysis of adhesion and biofilm formation on hydrophilic and hydrophobic surfaces of clinical isolates of Staphylococcus epidermidis

Abstract

Staphylococcus epidermidis is now well established as a major nosocomial pathogen associated with infections of indwelling medical devices. The major virulence factor of these organisms is their ability to adhere to devices and form biofilms. However, it has not been established that adherence and biofilm formation are closely linked phenotypes for clinical isolates. In this study, the initial adhesion to different materials (acrylic and glass) of 9 clinical isolates of S. epidermidis, along with biofilmpositive and biofilm-negative control strains, was assayed using physico-chemical interactions to analyze the basis for bacterial adherence to the substratum. X-ray photo electron spectroscopy (XPS) analysis of the cell surface elemental composition was also performed in an attempt to find a relationship between chemical composition and adhesion capabilities. Biofilm formation on the two surfaces was evaluated by dry weight measurements. Human erythrocytes were used to evaluate the ability of S. epidermidis strains to cause hemagglutination, an indicator of the production of a poly-N -acetyl glucosamine cell surface polysaccharide also involved in biofilm formation. The clinical isolates exhibited different cell wall physico-chemical properties, resulting in differing abilities to adhere to surfaces. Adhesion to hydrophobic substrata for all strains occurred to a greater extent than that to hydrophilic surfaces. Bacterial cell hydrophobicity seemed to have little or no influence on adhesion. X-ray photoelectron spectroscopy analysis showed a high ratio of oxygen/carbon for all strains, which is a common characteristic of S. epidermidis species. No relevant relationship was found between XPS data and adhesion values. All strains forming biofilms were able to agglutinate erythrocytes. However, no direct relationship was found between the amount of biofilm formed and the initial adhesion extent. These results indicate that high levels of initial adherence do not necessarily lead to thick biofilm formation. 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 S. epidermidis causing device-related infections.

Biofilm formation of Brazilian meticillin-resistant Staphylococcus aureus strains: prevalence of biofilm determinants and clonal profiles

“…This fact is corroborated by previous studies (Cerca et al, 2005;Sousa et al, 2009) and suggests that other cell surface factors, such as bacterial adhesins, can contribute to the initial adhesion process. However, when the evaluation was carried out according to the SCCmec type, strains harbouring SCCmec types III and IV were more weakly hydrophilic and adhered better than SCCmecII strains.…”

“…The haemagglutination assay was performed as described previously (Cerca et al, 2005) with some modifications. Human blood collected with EDTA was used to retrieve erythrocytes, by adding 5 ml of blood to 45 ml of saline solution, which was then centrifuged twice at 2500 g for 10 min.…”

The role of cell-surface interactions in bacterial initial adhesion and consequent biofilm formation on nanofiltration/reverse osmosis membranes

“…Experimental studies where both initial adhesion rate and biofilm formation rate were measured under comparable conditions are rarely found in the literature, showing a need for further investigation of the relationship between initial adhesion and biofilm formation. From the few studies that exist, it is generally accepted that there is no direct correlation between the levels of initial adhesion and the amount of biofilm formed [10][11][12]. A low adhesion rate might delay biofilm formation, but not prevent it [13].…”

The impact of material properties, nutrient load and shear stress on biofouling in food industries

“…was observed that for 80% of the successfully predicted cases, the impact of the tested variables at 0.5 h (initial adhesion) was further amplified during the biofilm maturation phase (after 6 h). Different studies have shown that lower initial cell adhesion leads to lower amount of biofilm (Cheng et al, 2007;Godoy-Gallardo et al, 2014) whereas others report that these initial events are not always important for biofilm maturation (Bernstein et al, 2014;Cerca et al, 2005).…”