Heterogeneity of Biofilms Formed by NonmucoidPseudomonas aeruginosaIsolates from Patients with Cystic Fibrosis

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Abstract
Biofilms are thought to play a key role in the occurrence of lung infections byPseudomonas aeruginosain patients with cystic fibrosis (CF). In this study, 20 nonmucoidP. aeruginosaisolates collected during different periods of chronic infection from eight CF patients were assessed with respect to phenotypic changes and in vitro biofilm formation. The physiological alterations were associated with a loss of motility (35% were nonmotile) and with decreased production of virulence factors (pyocyanin, proteases) and quorum-sensing molecules (45% of the isolates were unable to produce 3-O-C12-homoserine lactone quorum-sensing molecules). Compared with wild-type strain PAO1, mostP. aeruginosaisolates demonstrated different degrees of reduction of adherence on polystyrene surfaces. The in vitro biofilm formation of isolates was investigated in a hydrodynamic flow system. Confocal laser scanning microscope analysis showed that the biofilm structures of theP. aeruginosaisolates were highly variable in biomass and morphology. Biofilm development of six genotypically identical sequential isolates recovered from a particular patient at different time points of chronic infection (20 years) and after lung transplantation demonstrated significant changes in biofilm architectures.P. aeruginosabiofilm formation followed a trend of decreased adherence with progression of the chronic lung infection. The results suggest that the adherent characteristic of in vitro biofilm development was not essential for the longitudinal survival of nonmucoidP. aeruginosaduring chronic lung colonization.