, 2011). Clinically, in the chronic lung infection

associated with cystic fibrosis (CF), SCH727965 nmr the majority of aggregated P. aeruginosa are not found attached to pulmonary epithelial surfaces, but within the viscous mucus associated with larger airways (Worlitzsch et al., 2002; Bjarnsholt et al., 2009a). Therefore, although an elemental component of a biofilm is the aggregation of microbial cells, the necessity for attachment to a fixed substratum may be more elastic. Biofilms differ from single cells, and in bacterial systems, research has focused on differences in structure, function, and behavior. Structurally, the amassing of microbial cells has been compared with multicellularity (Stoodley et al., 2002) and constitutes a level of higher organization than single cells. As a strategy to help individual cells withstand diverse environmental conditions, phenotypic differentiation within a larger structure means functionally specialized cells to: (1) stick via different receptor–ligand interactions to a surface or to other cells (homotypic or heterotypic), (2) produce EPS, (3) metabolize slowly or rapidly grow, or (4) stay attached or disperse (Hall-Stoodley

et al., 2004). Definitions of biofilms also include ‘embedded in an extracellular polymeric matrix of microbial DNA Damage inhibitor origin.’ However, ‘extramicrobial’ host-derived components are particularly important in complex host environments such as dental plaques or intravenous catheter biofilms. Dental biofilms, for example, may use saliva proteins in the surface pellicle to attach to the tooth; bacteria may bind to fibronectin on medical implants; and microbial vegetations in infective endocarditis may be found enmeshed in a mass of fibrin, aggregated platelets, and other host proteins (Parsek & Singh, 2003; Diaz et al., 2006; Moter et al., 2010, Marsh et al., 2011; Stoodley et al., 2011). Restricting a definition of biofilm to ‘microbial or bacterial origin’ therefore ignores infections where bacteria

interact with host molecules and receptors to attach, replicate, and aggregate. Therefore, a more comprehensive definition of a clinically Epigenetics inhibitor relevant biofilm is: ‘aggregated, microbial cells surrounded by a polymeric self-produced matrix, which may contain host components. Cells in microbial biofilms additionally differ from planktonic cells in two major ways: (1) they are usually more tolerant of antibiotics and antimicrobial treatment, and (2) they may persist in the host, often despite a heavy influx of inflammatory cells and effector functions of the adaptive immune response. This distinction cannot be demonstrated in a diagnostic sample by culture alone, illustrating why better diagnostic markers, which exploit the difference between planktonic and biofilm cells, are needed. The clinical importance is that biofilm infections are typically chronic infections. and the presence of chronic and recurrent infection in a patient should raise the clinician’s suspicion of a biofilm infection.