A number of methods have been developed for cultivation and quantification of biofilms [12], Seliciclib chemical structure but no standardized protocol for assessment of biofilm formation has been established so far. Nevertheless, the microtiter plate method remains among the most frequently used assays for investigation of biofilm formation, and a number of modifications have been developed for the cultivation and quantification of bacterial

biofilms [33]. Since S. maltophilia biofilm formation on abiotic surfaces is generally considered less relevant than biofilm formation on cultured epithelial cells or in vivo, in this study we assayed biofilm formation onto an abiotic surface and compared the results to the ability of our S. maltophilia strains to form biofilm on IB3-1 cells, as assessed by quantitative colony counts. In agreement with previously reported experiments [20, 34], all the twelve S. maltophilia clinical isolates tested were able to form biofilm on both polystyrene and this website IB3-1 cultured epithelial cells. However, no correlation was found between quantitative biofilm formation on the abiotic surface and qualitative

biofilm formation on cultured cell monolayers, thus suggesting that the microtiter plate assay may not be predictive of the ability of S. maltophilia to form biofilm in vivo. Several explanations may account for this discrepancy. The crystal violet assay is surely a less specific method, and it is likely that the dye might also stain negatively charged extracellular molecules, including cell surface molecules and polysaccharides present in the extracellular matrix in mature biofilms, thus influencing the outcome of the test. Further studies are certainly needed to clarify Mephenoxalone this point. Recent

studies from different laboratories have highlighted the importance of interspecies bacterial interactions in influencing bacterial virulence and response to antibiotic therapy, both in pulmonary infections of CF and non-CF patients [35, 36]. In CF patients, there are several lines of evidence indicating the presence of a mosaic of diverse bacteria so that infections of CF pulmonary tissues are usually considered always polymicrobial [37]. Recently, Ryan et al. [38] have reported that the presence of S. maltophilia significantly influences, as through the synthesis of a diffusible signal factor, the architecture of P. aeruginosa biofilm formation and augments its susceptibility to polymyxins, recently re-introduced into clinical practice as anti-pseudomonal agents. In general, S. maltophilia is very often co-isolated with P. aeruginosa from CF patients [6, 25, 39, 40] and it has been hypothesized that infection by P. aeruginosa may enhance the chance of S. maltophilia to colonize CF pulmonary tissues [12, 13]. If this is true, it is reasonable to hypothesize that P. aeruginosa might enhance the ability of S. maltophilia to adhere to and/or invade CF pulmonary tissues.