Capacity of multidrug-resistant clinical isolates of Acinetobacter baumannii to form biofilm and adhere to epithelial cell surfaces

This study evaluated the capacity of 23 multidrug-resistant (MDR) clinical isolates of Acinetobacter baumannii to adhere to respiratory epithelial cell surfaces and to form biofilm on a polystyrene surface. All 23 A. baumannii isolates were capable of adhering efficiently to respiratory epithelial cells, and biofilm production was positively associated with epithelial cell adhesiveness (r 0.80, p < 0.0001). In the presence of the chelating agent EDTA, biofilm formation was markedly reduced. Cell adhesiveness and biofilm formation were significantly higher in isolates carrying the bla(PER-1) gene as compared with isolates without this extended-spectrum beta-lactamase gene (p < 0.005 and p < 0.001, respectively). Further examination by RT-PCR showed a positive correlation between the level of expression of the bla(PER-1) gene and the level of biofilm formation (r 0.89, p < 0.0001) and cell adhesiveness (r 0.74, p < 0.006). Overall, the study demonstrated a high capacity of clinical isolates of MDR A. baumannii to form biofilm and to adhere to respiratory epithelial cells. This feature, combined with multidrug resistance, might contribute to the survival of these organisms and their dissemination in the hospital environment.