Biofilm formed by S. maltophilia sequential strains isolated from the same CF patient. A. Biofilm formation on polystyrene, assessed by microplate colorimetric assay. PFGE analysis revealed that all strains belonged to the same pulsotypes 23.1. *** p < 0.001, Sm192 vs other strains, ANOVA-test + Bonferroni's multiple comparison test. B. CLSM examination of biofilm formed by sequential isolates belonging to pulsotype 23.1 after 24 h of development. C. CLSM examination of S. maltophilia Sm192 biofilm after 24 h of development. Orthogonal images, collected within the biofilm as indicated by the green and red lines in the top view, showed that biofilm consisted of cells forming a multilayered structure (red, propidium iodide-stained) embedded in an abundant extracellular polymeric substance (blue, concanavalin A-stained). Image capture was set for simultaneous visualization of both red and blue fluorescence. Magnification, ×100.