Pathogenic Effects of Biofilm on Pseudomonas Aeruginosa Pulmonary Infection and Its Relationship to Cytokines

BACKGROUND: An animal (Sprague-Dawley rat) model of Pseudomonas aeruginosa biofilm associated with chronic pulmonary infection in vivo was established and the effects of the biofilm on P. aeruginosa and its relationship to cytokines were investigated. MATERIAL/METHODS: Biofilm of P. aeruginosa in alginate beads and planktonic PA0725 were purified by anion-exchange chromatograph. Sprague-Dawley (SD) rats were immunized with the biofilm and then inhaled the same strain of P. aeruginosa. Anti-biofilm antibody titer was detected using the enzyme linked immunosorbent assay (ELISA) method. The cell count and differential count in the bronchoalveolar lavage fluid (BALF) were measured. The levels of cytokines (IL-17, IL-1β, MIP-2, and G-CSF) and tumor necrosis factor (TNF)-α in sera were also measured using an ELISA kit. RESULTS: The sera anti-biofilm IgG antibody titer of immunized SD rats was increased significantly on the 5(th) and 8(th) days after inhalation. The IL-17 concentration was significantly higher on the 8(th) day after inhalation. The results indicated that when biofilm-pre-immunized rats were challenged with inhalation of PA0725 of P. aeruginosa, the biofilm acted as an antigen substance and mediated the antibody reaction of the antigen, which might cause serious airway inflammatory response and lung tissue injury. This effect may be related to IL-17. CONCLUSIONS: P. aeruginosa biofilm protected the bacterium from antibiotics and might induce host immune damage in lung tissue and facilitate bacterium evading the host barrier.