To investigate the effects of macrolides on the formation of
Pseudomonas aeruginosa biofilm, the viable bacterial counts
and scanning electron microscopy of biofilms were performed. Comparing with the biofilm untreated with antibiotics, the viable bacterial counts of biofilms pretreated with 2mg/L azithromycin or 2mg/L erythromycin were reduced from 10 10 CFU/cm 2 to 10 3.3 or 10 3.7 CFU/cm 2. The combinations of azithromycin (2mg/L) with ceftazidime (0.0625mg/L), imipenem (0.5mg/L), meropenem (0.25mg/L), amikacin (0.0625mg/L) or ciprofloxacin (0.004mg/L) could reduce the viable bacterial counts of biofilms to 10 1.5 ~10 3.8 CFU/cm 2, and the combinations with erythromycin reduced the viable bacterial counts to 10 2.8 ~10 5.5 CFU/cm 2. Neither did midecamycin (32mg/L) alone nor combinations with anti
pseudomonas aeruginosa antibiotics show efficacy against formation of P.
Aeruginosa biofilms, the viable bacterial counts of biofilms varied from 10 9.3 to 10 11.5 CFU/cm 2. The results of scanning electron microscopy were comparable with those of the viable bacterial counts. These results indicated that azithromycin and erythromycin can prevent P.aeruginosa from forming biofilm; midecamycin and antipseudomonas aeruginosa antibiotics have no such effect on biofilm formation of P.aeruginosa .