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(335b) Electrochemical Detection of Pseudomonas Aeruginosa in Human Wound Exudate for Point-of-Care Applications

Authors: 
A significant limitation to antibiotic stewardship and improved patient care is the delay between the obtainment of a biological sample and its bacterial identification in the clinical setting. The use of plate cultures inoculated from swab samples is currently the standard practice for positive identification. Because this process can take anywhere from 24 to 48 hours before a positive result can be produced, there is an unmet need to develop rapid alternatives for bacterial identification. In clinical care, Pseudomonas aeruginosa is one of the leading causes of bacterial infections among patients with cystic fibrosis or compromised immune systems. Given the increasing prevalence of this highly resistant pathogen and the significant delay in care as a result of current bacterial identification practices, a rapid alternative would allow a physician to switch from broad-spectrum antibiotics to more direct targeted therapy, lowering antibiotic resistance and improving patient care outcomes.

To address this need, we report the use of an inexpensive, electrochemical sensor to detect pyocyanin, a unique, quorum sensing molecule secreted by Pseudomonas aeruginosa, in human wound exudate obtained from patients with chronic wounds. Because pyocyanin is redox-active, it can be detected using electrochemical sensors. This method eliminates sample preparation, takes less than two minutes to perform, and only requires 7.5 microliters of sample to analyze.

A total of 14 wound fluid samples were obtained from 12 patients enrolled in the Wound Etiology and Healing Study (WE-HEAL) at George Washington University. Wound effluent specimens were collected from swabs using the Levine technique. After collection, the swabs were placed in 0.65 µm pore size filters and centrifuged at 12,000 rpm for 4 minutes to remove cellular and fibrinous debris and to extract wound exudate. The samples were then stored at -80 °C until analysis. For each test, 7.5 µL of wound exudate was pipetted onto a screen-printed electrochemical sensor and square-wave voltammetry was used to determine the presence or absence of pyocyanin in the samples. The electrochemical results were compared against 16S rRNA profiling, one of the gold standards for bacterial identification. The electrochemical results yielded 9 correct matches, 2 false negatives, and 3 false positives, giving a sensitivity of 71% and specificity of 57% for detection of Pseudomonas aeruginosa. The results from this study will be used in improving the current sensor design and validating the use of an electrochemical sensor as a point-of-care diagnostic for detecting Pseudomonas aeruginosa. More importantly, the sensor can be functionalized to potentially detect other bacterial species by altering the applied potentials and thus can be enhanced into a point-of-care device with the capability to detect a wide range of clinically relevant bacterial pathogens.