(194g) Understanding the Effects of Ultrasound on Pseudomonas Aeruginosa bacterial Biofilms

Bacterial infections kill millions of people each year and cost billions of dollars to the global healthcare economy. By 2050 we may be unable to control lethal infections. The challenges in treatment stem from the biofilm around bacterium. Antibiotics are adsorbed, complexed, inactivated, or diluted within the biofilm, which promotes antibiotic immunity. Alternative treatment methods for infectious diseases are required. We propose the use of biomedical ultrasound – a non-invasive mechanical stimulus capable of inducing cavitation (i.e., bubble motion) and enhancing drug therapies. Yet, it is unknown how such mechanical stimulation affects the bacterial colonies and biofilm. Furthermore, there are no safe and clinically-viable ultrasound technologies to treat medical bacterial infections.

Here we focus our attention on Pseudomonas Aeruginosa bacterial biofilms, which are the leading cause of nosocomial infections. Here, we investigate the influence of ultrasound and ultrasound-induced cavitation on the mechanical properties of biofilms produced by P. aeruginosa. We present a novel means of growing biofilms on acoustically transparent substrates. With this in vitro model of PA01 wild strain grown on an acoustically transparent substrate, we expose the biofilms to varying ultrasound driving frequency and pressure amplitude with and without the presence of cavitation (i.e., ultrasound driven bubble dynamics). We monitor cavitation continuously and non-invasively with a passive cavitation detector. The biofilms are stained with live/dead assay after the exposure to ultrasound and the changes in their morphological behaviour is then characterized with epifluorescent and confocal microscopy. By understanding how ultrasound affects these bacterial communities will enable us to develop ultrasound-enhanced strategies for the treatment of medical biofilms.