Effect Of Low-Frequency Ultrasound In Combination With Ciprofloxacin On Bacterial Killing Of Pseudomonas Aeruginosa Biofilms And Its Structure

PartⅠ: Effect of low-frequency ultrasound in combination with ciprofloxacin on bacterial killing of Pseudomonas aeruginosa biofilms【Objective】To investigate the effect of low-frequency ultrasound in combination with ciprofloxacin on bacterial killing of Pseudomonas aeruginosa biofilms.【Methods】Rapid identification of biofilm by silver Staining, and these models of 6d PAO1 BF were divided five groups: control group, low-frequency ultrasound group (LUS), ciprofloxacin group (CF), ciprofloxacin prior to low- frequency ultrasound exposure group (CF +LUS) and low-frequency ultrasound irradiation prior to ciprofloxacin administration group (LUS+CF), then the metabolic activity of the bacteria inside BF was measured by XTT colorimetric assay.【Results】PAO1 biofilm can be saw on the surface of the polyethylene slices by silver Staining. The five groups of data of OD450 by XTT colorimetric assay were 2.30±0.55, 2.71±0.80, 2.57±0.70, 1.48±0.50, 1.63±0.50, respectively, P<0.05. The result showed that there were no significant differences among the control group, CF group and LUS group (P>0.05). There were significant differences in CF+LUS group and LUS+CF group compared with the other groups respectively (P<0.05), there was no significant difference between CF +LUS group and LUS+CF group (P>0.05).【Conclusion】Low-frequency ultrasound have no effect on BF, but it in combination with ciprofloxacin could be effective on the bacterial killing of Pseudomonas aeruginosa BF.PartⅡ: Effect of low-frequency ultrasound in combination with ciprofloxacin on the structure of Pseudomonas aeruginosa biofilms【Objective】To investigate the effect of low-frequency ultrasound in combination with ciprofloxacin on the structure of Pseudomonas aeruginosa biofilms, and to approach its mechanism preliminarily.【Methods】In vitro models of 6d PAO1 BF were established, and these models were divided five groups: control group, low-frequency ultrasound group (LUS), ciprofloxacin group (CF), ciprofloxacin prior to low- frequency ultrasound exposure group (CF +LUS) and low -frequency ultrasound irradiation prior to ciprofloxacin administration group (LUS+CF), the treated BF was stained by SYTO9/PI, monitored by Confocal Laser Scanning Microscopy (CLSM), quantification of the effect be calculated by Image Structure Analyzer (ISA) software; the structure of the BF was detected by Scanning Electron Microscope (SEM).【Results】The result of the thickness, the areal porosity, the average diffusion distance and the textual entropy showed that there were no significant differences among the control group, CF group and LUS group (P>0.05). The thickness of BF in CF +LUS group and LUS+CF group got thinner, the areal porosity was increased, the average diffusion distance and the textual entropy were reduced, there was significantly different between the two groups and the other three groups (P<0.05); The thick BF was detected by SEM in LUS and CF, the BF were diminished after treating by low-frequency ultrasound in combination with ciprofloxacin.【Conclusion】Low-frequency ultrasound have no effect on the structure of BF, but low-frequency ultrasound in combination with ciprofloxacin could be effective on the bacterial killing and destroying the structure of Pseudomonas aeruginosa BF.