© 2011 Wichtig Editore - ISSN 0391-3988 Int J Artif Organs ( 2011; : 9) 832-839 34 832 INTRODUCTION The broad and steadily growing use of implant devices in various medical fields has progressively been accompa- nied by the emersion of new opportunistic pathogens, in first place among them staphylococci, often capable of developing difficult to treat prosthetic infections (1-4). In Staphylococcus epidermidis, a main coagulase-negative Staphylococcus (CNS) implicated in implant-related infec- tions (5) PIA (see below), encoded by icaADBC locus, was initially suggested to be the only virulence determinant of Exopolysaccharide production by Staphylococcus epidermidis and its relationship with biofilm extracellular DNA Davide Campoccia 1 , Lucio Montanaro 1,2 , Stefano Ravaioli 1,2 , Valter Pirini 1 , Ilaria Cangini 1,2 , Carla Renata Arciola 1,2 1 Research Unit on Implant Infections, Rizzoli Orthopaedic Institute, Bologna - Italy 2 Department of Experimental Pathology, University of Bologna, Bologna - Italy ABSTRACT Implant-related infections are difficult to treat because they are very often associated with biofilm- forming micro-organisms capable of resisting host immune defenses and surviving conventional anti- biotic treatments. In Staphylococcus epidermidis biofilm-forming strains, the polysaccharide intercel- lular adhesin (PIA), whose expression is encoded by the icaADBC operon, is recognized as a main staphylococcal accumulation mechanism. Nevertheless, various observations have shown that PIA expression is dispensable and a variety of additional/alternative accumulation mechanisms, including extracellular DNA (eDNA) and several other factors of proteic nature, can compensate for icaADBC low expression or even for its absence. A suggestive hypothesis points to the possibility that changes in biofilm extracellular matrix composition can be induced in different environmental niches. In this study we aimed at investigating the relationship between the exopolysaccharide and eDNA biofilm components, screening 55 S. epidermidis clinical isolates by means of a simple fluorescence-based microtiter-plate assay. Our findings indicate the existence of a certain degree of correlation, although not a strict one, between eDNA and the exopolysaccharide component. The presence of exopolysac- charide greatly varied even in strains belonging to the same strain type determined by automated riboprinting. KEY WORDS: Implant infections, Staphylococcus epidermidis, Biofilm, Exopolysaccharide, Extracel- lular DNA Accepted: August 31, 2011 ORIGINAL ARTICLE biofilm (5, 6). Two essential characteristics common to most bacterial biofilms are intercellular aggregation and the presence of extracellular polymeric substances (EPS). Polysaccharide intercellular adhesin (PIA), a linear exopoly- saccharide consisting of β(1,6)-linked N-acetyl-glucos- amine residues (7), has long been known as the principal EPS in biofilm-forming S. epidermidis strains, although it was initially recognized under different names. In fact, at an early stage PIA was variously termed by different authors by the names of poly-N-acetyl-glucosamine (PNAG) and capsular polysaccharide adhesin (PS/A), which have re- DOI: 10.5301/ijao.5000048