Date of Award

Spring 2009

Document Type

Restricted Thesis

Terms of Use

© 2009 Sunjay Barton. All rights reserved. Access to this work is restricted to users within the Swarthmore College network and may only be used for non-commercial, educational, and research purposes. Sharing with users outside of the Swarthmore College network is expressly prohibited. For all other uses, including reproduction and distribution, please contact the copyright holder.

Degree Name

Bachelor of Arts


Biology Department


Biofilms are communities of microbes that adhere to a surface by means of a secreted polymeric matrix. The formation of antibiotic resistant biofilms on internal biomedical devices has contributed to a recent growth in the number of pernicious nosocomial infections (Ikeno, 2007). Ultrasound has been previously demonstrated to kill planktonic bacteria via oxidation, DNA damage and membrane disruption (Vollmer, 1998). In order to study the destructive effect of insonification on biofilms, we have developed three biofilm growth systems that incorporate ultrasonic transducers for direct delivery of ultrasonic energy to the biofilm. E. coli and P. aeruginosa biofilms were grown for 18-24 hours under a continuous flow of growth medium. Subsequently, biofilm destruction by insonification was observed in real time by confocal microscopy. Insonification at 810 kHz for 10 minutes at a O.2V power level is sufficient to remove approximately 50% of P. aeruginosa biofilm density from a glass microscope slide, and up to 90% removal is possible using a 0.6 V power level. Pre-treatment with low levels of the antibiotics chloramphenicol or tetracycline results in greater effectiveness of ultrasound in destroying the biofilm. We conclude that insonification in combination with other antimicrobial agents may be a useful tool for removing biofilms from medical and environmental systems.