Abstract: AIM: To investigate the combined effects of clarithromycin and gatifloxacin on experimentalPneumonia withPseudomonas aeruginosa in rats as a model for biofilm-associated infection.METHODS: The rat models of biofilm associatedPulmonary infection were created,and then were divided into 4 groups:models,clarithromycin(100mg·kg^-1),gatifloxacin(25mg·kg^-1),and clarithromycin(100mg·kg^-1)+gatifloxacin(25mg·kg^-1).The changes ofPathology,bacteriology and immunology were observed.RESULTS: After the treatment of clarithromycin combined with gatifloxacin,the bacterium inlung were almost cleaned,and the antibody in serum to bacteria returned to normal.The changes ofPathology were restored.CONCLUSION: The combination of clarithromycin andlevofloxacin has synergism in treating biofilm-associated chronic respiratory infection in animal models.

Key words: pharmacology, clarithromycin, gatifloxacin, bacterial biofilms, combination drug therapy