(237b) Improving Sensitivity of Electrochemical Sensors for Detecting Virulence Factors and Quorum Sensing Molecules in Pathogenic Bacteria

Authors: 
Kimani, M., Northeastern University
Sismaet, H. J., Northeastern University
Goluch, E. D., Northeastern University
Improving sensitivity of electrochemical sensors for detecting virulence factors and quorum sensing molecules in pathogenic bacteria

Martin Kimani, Dr. Edgar Goluch, Department of Chemical Engineering, Northeastern University, Boston, MA

Microbiologists in the research and biotech industry still primarily depend on bacterial culture plates to identify bacterial species. In the clinical setting, a patient swab sample is submitted for identification which can take 1 â?? 5 days before the clinicians can confirm a bacterial infection and provide the required antibiotic to the patient; this delay in acquiring results can hinder patient care especially with the growing impact of antibiotic resistant bacteria. Similarly during the production of biotech medications, bioreactor samples are submitted for offline analysis to monitor potential bacterial contaminations with results received anywhere from 1 â?? 5 days after sample submission; this delay in acquiring bacterial contamination results can hinder production and negatively impact product supply to the patients. There are existing bacterial identification methods that reduce the time to acquire results from days to hours with improved sensitivity such as genetic identification using polymerase chain reaction (PCR) and other molecular methods that detect DNA hybridization. However, these technologies require costly equipment and therefore are not economically scalable for portable bacteria detection or for in-process monitoring of bioreactor contamination.

Our proposed technology provides an alternative low cost and real time bacterial detection to improve patient care and potential to provide in-line bacterial process monitoring. The technology uses low cost electrochemical sensors for detecting the redox active bacterial or molecular markers that bacteria excrete as virulence factors and for quorum sensing (QS). QS is a form of inter-cellular communication that bacterial species use to regulate gene expression and to synchronize multicellular activity. Our lab has previously used electrochemical sensors to detect one of the redox active virulence factors named pyocyanin that is produced by the clinically relevant bacteria Pseudomonas aeruginosa. The concentration of the pyocyanin was correlated to be proportional to the bacteria density. Therefore, the sensitivity of the sensors are limited to the relevant cell density.

In this work we explore how the sensitivity of the electrochemical sensors can be improved for detecting virulence factors and quorum sensing molecules in extremely low cell density states as those found in early bacterial infection and early bioreactor contamination cases. Tangential flow filtration coupled with forward osmosis was utilized to concentrate different species of bacteria cultures and redox active molecules in a flow reactor. Low cost electrochemical sensors were developed and used for in-process monitoring of the electrochemical activity of the concentrated cultures and redox active molecules. This work explores if and to what limits a low electrochemical signal from low concentrations of redox active molecules in a sample volume can be increased by forward osmosis.

The results from this work could provide the ability to detect virulence factors and quorum sensing molecules in extremely low concentrations similar to the concentrations that may be found during the onset of bacterial contamination. In addition, the improved electrochemical sensitivity from this work can allow for screening other bacterial species to identify if they produce extremely low concentrations of quorum sensing molecules and virulence factors that could be detected using electrochemical sensors.