S. aureus is an important human pathogen associated with numerous skin diseases including chronic-wound infections. S. aureus produces a wide range of virulence factors including hemotoxins, pore forming toxins, and superantigens (e.g. toxic shock syndrome toxin-1, Staphylococcal enterotoxin). The impact of biofilm formation on S. aureus virulence is controversial. In one study, virulence factor gene expression in S. aureus cells within a biofilm was shown to be downregulated when compared to planktonic S. aureus cultures [2]. Another study showed that biofilm formation had no effect on the virulence of S. aureus [9], while several studies highlight the

necessity of regulatory Selleck C59 wnt elements associated with biofilm formation on the regulation of virulence [10, AZD1480 11]. Human keratinocytes (HKs) are the

most abundant cell type in the epidermis and are essential for wound healing. HKs are constantly exposed to bacterial stimuli and function in innate immunity through the formation of a physical barrier to the external environment and the recognition of conserved pathogen associated molecular patterns (PAMPs). Examples of PAMPs include the bacterial cell wall components peptidoglycan and lipoteichoic acid, bacterial DNA, flagella, and other conserved structures [12]. PAMPs are recognized by cell surface receptors called toll like receptors (TLRs) which are found on a variety of cell types including professional immune cells, endothelial cells, and cells of the epidermis. HKs express functional TLRs making them the first line of defense against bacteria in the skin [13]. HK activation induced by TLRs in response to bacterial stimuli is mediated in part by mitogen activated protein kinase (MAPK; specifically JNK, p38, and ERK) cascades resulting in the production of inflammatory cytokines [14–16]. MAPKs are major components regulating the pathology of chronic

inflammation, diabetes mellitus, Cyclooxygenase (COX) and other chronic diseases [17, 18]. The highly orchestrated production of inflammatory cytokines by HKs is an important initial step in a normal immune response. Derangement of cytokine production by bacterial infection can lead to chronic inflammatory conditions [19]. In this study, we investigated the transcriptional response of HKs exposed to S. aureus biofilm conditioned medium (BCM) and planktonic conditioned medium (PCM) to reveal genes associated with pathogenesis. We correlated microarray data with data from enzyme-linked immunoassays (ELISA) and enzyme inhibition assays, to delineate a biofilm specific response associated with inflammation in HKs and formulate a hypothesis for biofilm-induced click here pathogenesis in chronic wounds. Results Proteomic analysis of BCM and PCM A preliminary proteomic analysis of BCM and PCM revealed differential protein compositions.