Gene expression during S. epidermidis biofilm formation on biomaterials Jasmine D. Patel, 1 Erica Colton, 1 Michael Ebert, 2 James M. Anderson 1,3 1 Department of Biomedical Engineering, Case Western Reserve University, Cleveland, Ohio 2 Medtronic Inc., Minneapolis, Minnesota 3 Department of Pathology, Case Western Reserve University, Cleveland, Ohio Received 16 January 2012; accepted 17 January 2012 Published online in Wiley Online Library (wileyonlinelibrary.com). DOI: 10.1002/jbm.a.34221 Abstract: Biomaterial-centered infections are initiated by ad- hesion of bacteria to an implant, followed by colonization and mature biofilm formation. Staphylococcus epidermidis is com- monly identified as the cause of these device-centered infec- tions. This study used an in vitro model to evaluate temporal changes in the expression of genes—icaADBC, agrBDCA, aap, and atle—that have been identified to play a role in the patho- genesis of S. epidermidis infections. Real-time reverse tran- scription–polymerase chain reaction was used to determine changes in gene expression from S epidermidis biofilm grown on polyurethanes (Elasthane 80A, hydrophobic) modified with polyethylene oxide (Elasthane 80A–6PEO, hydrophilic) and fluorocarbon (Elasthane 80A–6F, hydrophobic). In vitro expression of the ica locus, which is involved in initial adhe- sion and intracellular aggregation, increased up to 100-fold from 2 to 48 h, whereas gene expression for autolysin AtlE decreased slightly from 2 to 12 h, followed by a 10-fold increase by 48 h. Upregulation of the aap gene associated with bacterial accumulation and the agr quorum-sensing system was observed during biofilm formation over 48 h. In addition, no correlation was observed between S. epidermidis gene expression and biomaterial surface chemistry. This study used an in vitro model to demonstrate that enhanced expression of the atle, aap, agr, and ica genes plays an important role in initial foreign body colonization and potentially in the establishment of a device-associated infection. V C 2012 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 00A: 000–000, 2012. Key Words: Staphylococcus epidermidis, biofilm, genetics, biomaterials How to cite this article: Patel JD, Colton E, Ebert M, Anderson JM. 2012. Gene expression during S. epidermidis biofilm formation on biomaterials. J Biomed Mater Res Part A 2012:00A:000–000. INTRODUCTION Biofilm formation on the surface of a biomaterial contrib- utes to the pathogenicity of cardiovascular device-centered infection. Persistence of infection can occur because of a compromised host immune response in the presence of a foreign implant and the high resistance of biomaterial-ad- herent bacteria to antibiotic therapy. The slime-forming pathogen Staphylococcus epidermidis is commonly identified as the cause of device-centered infections. 1–4 The formation of a biofilm occurs in a two-step process. The first step is rapid adhesion to an implant surface. The second step is the slower phase of bacterial accumulation, which involves proliferation, intercellular adhesion, and exo- polysaccharide slime formation, giving rise to a multilayered biofilm. 5–7 Several molecular moieties have been identified as being involved in the adhesion phase. Autolysin AtlE, encoded by atle gene, has been shown to mediate initial attachment to polystyrene. 8 A mutant strain of S. epidermidis lacking AtlE demonstrated reduced polystyrene attachment and vitronec- tin binding capabilities, and a reduced bacterial cell surface hydrophobicity. 8 The expression of capsular polysaccharide/ adhesin (PS/A) has been correlated to primary bacterial ad- hesion on catheter surfaces and intercellular adhesion nec- essary for the formation of biofilm. 9 PS/A, encoded by the icaADBC locus, is a high-molecular-weight N-succinylated b- 1-6-linked polyglucosamine. 10 During the accumulation phase, polysaccharide intercel- lular adhesin (PIA), also encoded by the icaADBC locus, has been shown to mediate intercellular adhesion and bacterial accumulation. 11–14 PIA is considered to be a significant viru- lence factor in the pathogenesis of S. epidermidis catheter- related infection in animal models. 15,16 Another virulent fac- tor that plays a role in S. epidermidis pathogenesis is the accumulation associated protein (AAP), a 140 kDa protein isolated from S. epidermidis strains. 17,18 To establish an infection, S. epidermidis regulates the expression of groups of virulent genes using a quorum-sens- ing system that allows the pathogen to adapt to changing environmental conditions. The quorum-sensing systems reg- ulate virulence factors by production and recognition of pep- tide-based pheromones. The S. epidermidis accessory gene Correspondence to: J. M. Anderson; e-mail: jma6@case.edu V C 2012 WILEY PERIODICALS, INC. 1