Effects of azithromycin and clarithromycin on biofilm formation of Pseudomonas aeruginosa / 临床检验杂志

ABSTRACT

Objective To investigate the effects of azithromycin and clarithromycin on biofilm formation of Pseudomonas aeruginosa.Methods The minimal inhibitory concentrations (MIC) of azithromycin,clarithromycin,ceftazidime,ciprofloxacin and gentamicin against 4 strains of Pseudomonas aeruginosa (ATCC 27853,PA1,PA2 and PA3) were determined by broth microdilution method.The biofilm formation of Pseudomonas aeruginosa was identified by silver dyeing method on the biofilm model with medical microporous membranes in vitro.The effects of azithromycin and clarithromycin on the adhesion of biofilm were detected by crystal violet staining.The synergistic bactericidal effects of azithromycin and clarithromycin with ceftazidime,ciprofloxacin or gentamicin were detected by thiazolyl blue method respectively.Results The MIC values of Pseudomonas aeruginosa ATCC 27853,PA1,PA2 and PA3 for azithromycin,clarithromycin,cefiazidime,ciprofloxacin and gentamycin were 32,64,1,≤0.125 and 0.25 μg/mL;32,256,8,0.25 and 1 μg/mL;64,128,＞ 256,32 and 2 μg/mL and 64,128,8,2 and 0.25 μg/mL.The results of silver staining showed that the microfiltration membranes of all the four P.aeruginosa cultures appeared to be grayish black,thick and dense,and cotton-like.Compared with the control group in which no antibacterial drugs were added,both azithromycin and clarithromycin (1/16 or 1/4 MIC) reduced significantly the adhesion of the 4 strains of Pseudomonas aeruginosa (ATCC 27853,PA1,PA2 and PA3) on the microporous membrane (Pall ＜ 0.05).Compared with the use of 1 MIC of ceftazidime,ciprofloxacin or gentamycin alone,the combination of anyone of the four antimicrobial drug with azithromycin or clarithromycin (1/16 MIC) reduced the counts of viable bacteria on each biofilms with significant differences (P all ＜ 0.01).Conclusion Azithromycin and clarithromycin could effectively inhibit the biofilm formation of Pseudomonas aeruginosa and may present synergistic effects combined with cefiazidime,ciprofloxacin or gentamicin.