Bacteria are known to form complex extracellular matrices known as biofilms that allow them to adhere to multiple surfaces and thrive in diverse environments. With the growing presence of highly persistent bacterial species in the hospital setting, as recently identified by the Centers for Disease Control and Prevention, understanding biofilm growth will play a key role in combating antimicrobial resistance in modern day healthcare. Platforms and techniques for studying these bacteria as they adhere and grow on surfaces as well as strategies for their removal from surfaces can provide significant insight in preventing biofilm formation. To address these needs, a quartz crystal microbalance (QCM) was used to investigate bacterial biofilm growth and removal.
QCMs measure the precise oscillation of a quartz sensor at their resonant frequency when an alternating voltage is applied. A frequency shift response that is measured by the QCM in real time indicates either mass deposition or removal from the surface. These highly sensitive mass measurements can be used to monitor how bacteria adhere, grow, and form biofilms on surfaces.
Bacterial species Pseudomonas aeruginosa and Staphylococcus aureus were grown overnight in lysogeny broth growth media at 37 °C. Bacterial species were diluted and loaded into the QCM, where they were allowed to adhere and grow on the gold-coated quartz surface over the course of several hours. Changes in both frequency and damping were recorded to monitor bacterial accumulation on the surface. Once the bacterial cells were stably attached to the surface, an SDS detergent was loaded into the system to study the effect of biofilm removal. Biofilm removal was determined by the sensor’s response as it returned to the original baseline and confirmed by visual inspection using the device’s optical window. This study validates the use of a QCM for studying bacterial adhesion and removal from surfaces as well as investigating the effectiveness of biofilm removal agents.