Abstract:

 AIM: To investigate the effect and mechanism of Aztreonam combined Azithromycin on Pseudomonas aeruginosa ATCC 27853, and clinical separation of 15 strains of Pseudomonas aeruginosain vitro. METHODS: Broth dilution method and checkerboard dilution method were used to determine Aztreonam alone or in combination with Azithromycin on Pseudomonas aeruginosa ATCC27853 and 15 clinical isolates of Pseudomonas aeruginosa. Then, the biofilm formation of the clinical separation of 15 strains of Pseudomonas aeruginosa was identified by Congo red plate method. The crystal violet experiment was used to compare the ability of biofilm formation of Pseudomonas aeruginosa. Growth curve and viable count of Pseudomonas aeruginosa biofilm were investigated by continuous dilution method. The silver staining method was used to observe the biofilm of Pseudomonas aeruginosa by Aztreonam alone and in combination with Azithromycin. RESULTS: Azithromycin combined with Azithromycin on Pseudomonas aeruginosa ATCC 27853 showed synergistic effect; of the 15 isolates of Pseudomonas aeruginosa, 6 were synergistic, 6 additive, and 3 irrelevant. Congo red plate experiments show that the clinical separation of 15 strains of Pseudomonas aeruginosa, 12 strains can formed biofilm, 3 did not formed biofilm, and the rate of biofilm formation was 80%. The results of crystal violet experiment showed that the biofilm formation ability of 16091217 was the strongest when compared with other strains. The continuous dilution method of viable bacteria count experiment showed that the number of viable bacteria in Azithromycin group, Aztreonam group was significantly different compared with Azithromycin+Aztreonam group. The silver staining method showed that the inhibition effect of Azithromycin on the formation, early and mature stages of biofilm formation.CONCLUSION:The study found that the effect of Aztreonam combined with Azithromycin was mainly synergistic and additive in vitro. Aztreonam combined with Azithromycin presents synergistic bactericidal effect on Pseudomonas aeruginosa biofilm formation.

Key words: aztreonam, azithromycin, Pseudomonas aeruginosa, biofilm