Abstract: ObjectiveTo investigate the pathogenicity of biofilm of Pseudomonas aeruginosa.MethodsSixty guinea pigs were randomly assigned to three groups,and silicone tube enveloped by biofilm(biofilm group),planktonic bacteria (planktonic bacteria group),and normal saline(control group)were placed in trachea of the animals by tracheostomy,respectively.Fifteen days after silicone tube were placed,bronchoalveolar lavage fluid(BALF),bronchial and lung tissue samples were collected.The bacterial number was determined and biofilm formation ability of Pseudomonas aeruginosa isolated from the samples was examined.Histopathological changes of bronchial and lung were investigated with HE staining.ResultsThe incidence rate of chronic lower respiratory tract infection was 66.7% in biofilm group and significantly higher than that of in planktonic bacteria group(P<0.001).In biofilm group,the lung and bronchial tissue of guinea pigs showed changes such as fibrous material infiltration in alveolus,inflammatory cells infiltration in alveolar septa,bronchus cilia epithelium proliferation, and lymphocytes infiltration in submucosa.Meanwhile,in biofilm group,the total bacteria number in BALF an lung samples were 7.45±0.23×10³cfu/mL and 6.78±0.36×10³cfu/g,and Pseudomonas aeruginosa strains forming biofilm were also isolated.ConclusionPseudomonas aeruginosa biofilm is one of risk factor for chronic lower respiratory tract infection.