Objective: To study the influence of
erythromycin on the synthesis of biofilm in P.
aeruginosa and the ausceptibility
of P.
aeruginosa to antibiotics. Methods: 37 patients with P. aeruginosa lower respiratory infection were randomly enrolled into
erythromycin group ( n =22) or non erythromycin group ( n =15). Both groups received the same abtibiotic therapy except erythromycin. The quantity of alginate, the morphological changes of P. aeruginosa by transmision electron microscope were checked at the baseline and 10 days after treatment. Results: The quantity of alginate produced by P. aeruginosa reduced significantly in erythromycin group after erythromycin treatment compared with that at baseline <(22.5±6.72) μg/ml vs (16.8±6.21) μg/ml, P <0.01)>; while in non erythromycin group, the quantity of alginate increased significantly <(25.48±20.76) μg/ml vs (51.97±43.41) μg/ml, P <0.01>. The morphological changes of P. aeruginosa in erythromycin group showed marked edema of bacteria cells, rarefaction of cytoplasma, nuclear degenerateion, disappearance of bacterial fimbriae and flagella, the germs aggregated to form a mass. Conclusions: Erythromycin as an adjunct drug for the therapy of lower respiratory tract infection coused by P.aeruginosa , can inhibit the synthesis of alginate, and formation of liofilm, thus enhance the bactericidal activity of antibiotics.