Ultrasound Of Staphylococcus Aureus Biofilm In Vitro Study

Object: To study ultrasonic cavitation on common bacterium(Staphylococcus aureus) and its destructive effect on the biofilm of the bacterium.Methods: 1. Use the guidance plate cultivation method to establish an extracorporeal model of biofilm of staphylococcus aureus, which is divided into the control group(false irradiation), experimental group I(low intensity ultrasonic irradiation) and experimental group II(high intensity HIFU irradiation). Propidium iodide(PI) and FITC-Con A are respectively adopted to mark DNA and polysaccharide of the bacteria, and confocal laser scanning microscope is used to examine the molding of the bilfilm. 2. Ultrasonic oscillation- live bacteria counting method is adopted to evaluate the influence of ultrasonic cavitation on BF bacteria; Confocal laser scanning microscope is used to collect the images from different levels, the changes after the ultrasonic cavitation of biofilm and the bacteria will be observed.Results: 1. Ultrasonic oscillation- live bacteria counting method: the bacterial colonies of the control group, experimental group I and experimental group II are(5.12±0.81, 5.14±0.66, 3.97±0.43) lgcfu/cm3 respectively. According to the statistical analysis, there is no evident difference between the control group and the low intensity group, and there is a statistical difference between the control group and the high intensity group, between the low intensity group and the high intensity group. 2. According to the observation under the confocal laser scanning microscope, the number of EPS dyed with green fluorescence and the number of DNA of the cell nucleus dyed with red fluorescence have decreased. The higher the intensity is, the more the decreased amount is.Conclusion: The ultrasonic cavitation of low intensity can’t kill the bacteria and it has a small destructive effect on the biofilm of the bacteria; the ultrasonic cavitation of high intensity can effectively kill the bacteria and has an obvious destructive effect on the bilfilm of the bacteria.