(113e) Up-Regulation of Quorum Sensing Molecules for Early Electrochemical Detection of Bacterial Pathogens

Pseudomonas aeruginosa is one of the leading causes of gram-negative bacterial infection in the hospital setting and is an important bacterium to study given the nature of its prevalence and its impact on people with cystic fibrosis and compromised immune systems. Unique to this species is its production of pyocyanin, a redox-active quorum sensing molecule (QSM) linked to biofilm formation. Because it is redox-active, pyocyanin can be directly detected and monitored electrochemically. Previous research has shown that it possible to detect this QSM with very high sensitivity using microfabricated electrode assemblies. The development of these devices has ultimately led to a growing interest in their medical applications. One potential application is to elicit faster bacterial detection. Previous research has shown that P. aeruginosa biofilm formation can be regulated by adding in different amino acids. To further test this phenomenon, six different amino acids were chosen as means of up-regulating pyocyanin production by P. aeruginosa to achieve faster bacterial detection.

Individual amino acids (proline, histidine, arginine, leucine, tyrosine, and valine) were dissolved at specific concentrations in liquid cultures of P. aeruginosa containing either a M63 minimal media or trypticase soy broth (TSB). Using square-wave voltammetry, the production of pyocyanin was monitored electrochemically over a series of hours using disposable screen-printed carbon electrodes connected to an external Ag/AgCl reference.

The measured current versus applied voltage was recorded for each sample. As the amino acid additive varied, an increase in the maximum peak potential was observed with tyrosine and valine eliciting the strongest electrochemical response. Further analysis over the course of 24 hours of monitoring shows that cultures containing TSB elicited a faster response from pyocyanin production than the M63 media. The results from this study highlight the use of amino acids as up-regulatory molecules for faster bacterial detection. More importantly, the concept of using up-regulatory molecules for rapid detection schemes can be extended to virtually any pathogen.