Bacterial Adhesion and Interaction with Biomaterial Surfaces - Biointerfaces: Where Material Meets Biology - page 368

This adsorbed protein layer may minimize the effect of biomaterial surface
properties on bacterial adhesion 34,35 so that interactions between the bac-
teria and the proteins mediate bacterial adhesion. The serum proteins
generally suppress initial bacterial adhesion due to the lack of a specific
interaction between albumin and bacteria 36,37 while adhesive plasma pro-
teins such as fibrinogen (Fg) and fibronectin (Fn) were reported to con-
tribute to increase of bacterial adhesion. 35,38,39 This increase in bacterial
adhesion is believed to be due to specific ligand-receptor events
between plasma proteins and bacterial cell surface proteins known as
the microbial surface components recognizing adhesive matrix molecules
(MSCRAMM). 32,40-42 Multiple MSCRAMM found on the S. epidermidis sur-
face promote adhesion of bacteria including SdrG, 43,44 SdrF, 42,45 and extra-
cellular matrix binding protein (Embp), 41,46 which were identified to bind
Fg, collagen, and Fn, respectively. It has also been demonstrated that SdrG
promotes platelet adhesion/activation and aggregation. 47
Additional protein and polysaccharide components are also involved in
primary attachment to biomaterial surface. One of the most prominent ad-
hesion molecules is autolysin. Heilmann et al. first described autolysin, AtlE,
a 148 kDa protein in S. epidermidis which mediated attachment to poly-
styrene surface. 48 It is highly homologous to the autolysin/adhesin AtlA, a
137 kDa protein found in S. aureus. 49 Later, the other novel autolysin/
adhesin proteins were found in S. epidermidis (Aae) 50 and in S. aureus
(Aaa), 51 respectively. Both were identified as a 35 kDa surface-associated
protein that has bacteriolytic activity and binds vitronectin, Fg, and Fn. Not
only do these proteins have specific adherence functions, they also function
to release extracellular DNA (eDNA) which is found to be an important ad-
herence/aggregation factor in both S. epidermidis and S. aureus biofilm for-
mation. 52,53 Studies have shown that extracellular DNA is released by
different components on cell depending on species, and functions as a
structural support to maintain biofilm architecture. 54 Extracellular DNA
has also been demonstrated to chelate cations and induce antibiotic re-
sistance of biofilms. 55 In addition, non-proteinaceous adhesins, cell wall
teichoic acids, were also found to function as a bridging molecule between
S. epidermidis and Fn adsorbed polymer surfaces. 56 The features and
functions of surface and surface-associated protein adhesins as well as of
non-proteinaceous adhesins were recently reviewed. 57

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13.2.2 Accumulation and Proliferation of Bacterial Cells
Once the bacteria adhere to the surface of the foreign body, microorganisms
multiply and accumulate in multi-layered cell clusters. In this stage, most of
the biofilm bacteria produce extracellular polymeric substances (EPS) to
form the biofilm matrix. A specific polysaccharide antigen, termed poly-
saccharide intercellular adhesion (PIA), has been identified to be a major
functional component for intercellular adhesion and biofilm accumulation
in staphylococci. 58-60

Its importance in the biofilm production of