Treatment of bacterial biofilms on polymeric biomaterials using antibiotics and ultrasound.

New studies on the effect of frequency and duration of exposure upon the ultrasonic enhanced action of gentamicin against biofilms of Escherichia coli are presented in this paper. Ultrasound was applied at clinical levels which would not harm human tissue. The study on frequency indicated that lower frequencies produce higher levels of killing. The results of the timed experiment indicate that complete sterilization of a 14-h biofilm can be achieved after 6 h of exposure. These findings are significant because they show that biofilms can be reduced to zero reproductive ability as assessed by plate counting.