Intervention of azithromycin on Pseudomonas aeruginosa biofilm and virulence factors

Abstract

Objective To evaluate the effect of azithromycin on Pseudomonas aeruginosa PAO1 biofilm formation and virulence factors production. Methods Detect the minimum inhibitory concentration of azithromycin against PAO1 by 2-fold dilution method. Crystal violet staining assay was used for initial adhesion assays. The PAO1 biofilm was established in vitro and observed by scanning electron microscope. Viable bacterial counts were determined by serial dilution. LasB elastolytic activity was determined by using Elastin-Congo Red. Protease activity was determined by Azo-casein. Chloroform extraction method was used for pyoverdine assay . The orcinol assay was used to directly assess the amount of rhamnolipids . Results Scanning electron microscope biofilm and viable bacterial counts of PAO1 adhered to the surface of catheter in PAO1 azithromycin group were less than the PAO1 control group after incubated for 3 d and 7 d ( P ＜0.05), and the initial adhesion was weaker ( P ＜ 0. 05 ). The virulence factors production were obviously decreased (P ＜0.01 ). LasB elastolytic activity and pyoverdine were even reduced to the same as with the PA-JP3 group ( P ＞ 0.05 ), but the protease activity and the rhamnolipids concentration were higher than the PA-JP3 group ( P ＜ 0.05 ). Conclusion Azithromycin can inhibit PAO1 bioflim formation in vitro and virulence factors production. Key words: Pseudomonas aeruginosa ; Azithromycin ; Biofilm ; Virulence factors ;