Effects of subinhibitory concentrations of antibiotics on the biofilm formation of pseudomonas aeruginosa

Objective: To study the effects of the subinhibitory concentrations of four antibiotics on the biofilm formation of pseudomonas aeruginosa. Methods: 2 types of culture media of 1-broth (LB) and mueller–hinton broth (MHB) were used with the application of static biofilms model of pseudomonas aeruginosa. Results: (1) The results of the static-made biofilm were as follows: in the MHB media, azithromycin could induce the biofilm formation of PAO1 when the concentrations were more than 16ug/ml, but inhibited the biofilm formation when the concentrations were less than 8ug/ml.When the PAO1 was cultured in LB, azithromycin would induce the bioflim formation at the sub-MIC concentrations. Ciprofloxacin and ceftazidime could inhibited the biofilm formation at the sub-mic concentration. Amikacin could induce biofilm formation at the concentration of 0.125 and 0.25ug/ml cultured in MHB and LB respectively. All the results above had statistical diference compared with the blank. The Furanone C-30 was added in the static biofilm model with the azithromycin concentration 8ug/ml and 4ug/ml;the results had no statistical difference. (3) Silver staining results: when the concentration of azithromycin was 8ug/ml,the formation of the biofilm was the most, the second was blank and the the lest was 256ug/ml. Conclusions: The sensitivity of the azithromycin to the POAI was different with changing of the environment. Azithromycin could induce the biofilm formation at the subinhibitory concentration. Ciprofloxacin and ceftazidime could inhibit the biofilm formation; amikacin could induce the biofilm formation at the concentration of 0.125ug/ml and 0.25ug/ml.