Background

Detection of antibiotic drug susceptibility and resistance has become a global issue, and national as well as international health organizations have called for the urgent development of new diagnostic and treatment strategies. 

Currently, the most common antibiotic susceptibility/resistance testing methods (i.e. antibiotic susceptibility testing; AST) used in diagnostic labs rely on phenotypic detection (i.e. disk diffusion, microdilution, cultures etc.); methods which require analysis times ranging from hours to days. While there have been advances towards automation and use of new technologies such as MALDI-TOF and genomic sequencing, these methods rely on time- and cost-intensive methods and instrumentation. With the current market dominated by phenotypic detection methods, most emerging technologies are focused supplanting those methods.

There is currently no cost-effective, rapid, accurate, point-of-care diagnostic platform on the market for rapid screening of drug susceptibility/resistance. Development of such a platform has the potential to revolutionize infection treatment approaches by allowing for more rapid diagnosis, faster treatment and lower healthcare costs related to both acute and chronic diseases.

Technology Overview

Our current work takes an interdisciplinary and unconventional approach to detect antibiotic uptake and efflux to ultimately provide a tool for early detection of drug susceptibility in clinical samples. The technology consists of bioelectrochemical sensors to rapidly and reliably predict drug susceptibility/drug resistance in target cells. Our method for detecting drug susceptibility is based on 2 electrochemical techniques, voltammetry and impact chemistry. Both techniques provide information about the ability of cells (i.e. bacteria and cancer cells) to take up and retain therapeutic compounds.

Example: A large number of bacterial infections have become resistant to antibiotics due to the presence of drug efflux pumps on the bacterial cell membranes. These efflux pumps expel antibiotics rapidly from the cell interior, before cell viability is compromised.

Using linear sweep voltammetry, it is possible with our method to distinguish between drug susceptible (Figure 1A, blue line) and drug resistance (Figure 1A, red line). Bacteria are captured by a specific antibody at the electrode, exposed to an antibiotic of choice and drug retention in the bacterial cells can be detected within minutes. A higher electrochemical current signal is related to drug efflux from the bacteria, which increases the concentration of analyte at the electrode surface. Under this design, the signal will be compared to that obtained from a drug susceptible bacteria strain.

Similarly, pharmaceutical efflux can be detected from cancer cells. Furthermore, our recent peer-reviewed manuscript on drug uptake in cancer demonstrates the ability of electrochemistry to quantify pharmaceutical uptake in ovarian cancer. In this approach, cells are exposed to a pharmaceutical solution. Within 20 minutes drug susceptible bacteria remove the analyte from solution, resulting in a reduced electrochemical signal. Drug resistant cancer cells often exhibit cell membrane mechanisms to inhibit pharmaceutical uptake in cells. In this case, the measured electrochemical current signal will remain unaltered.

Alternatively, impact chemistry may also be used for our electroanalytical detection method. Under this design, free floating bacteria can be directly detected in a urine or blood sample via collisions with a metal wire that functions as electrode. When an antibiotic is added to a biological sample, bacteria that are drug resistant will result in current spikes greater than those seen in drug susceptible bacteria. This method offers the monitoring of drug susceptibility within seconds.

Both of these methods can provide critical information as to drug resistance in cells, with the technique chosen dependent on the type of cells examined (bacterial vs cancer cells) and their clinical presentation (i.e. within tissues vs body fluids). However, both detection techniques can be incorporated into a portable potentiostatic device, employing disposable screen printed electrodes which can be applied to biological samples.

Current sensor proof-of-concept development is focused on antibiotic susceptibility/resistance, with R&D focused on, a) validation of the detection method using impact chemistry; b) maximizing sensitivity and selectivity of the system, and; c) validation studies targeting clinically relevant target pathogens.

**Publication:**Kuss, Sabine & Luu, Huy & Nachtigal, Mark. (2020). Electrochemical characterization of carboplatin at unmodified platinum electrodes and its application to drug consumption studies in ovarian cancer cells. Journal of Electroanalytical Chemistry. 872. 114253.

Benefits

Currently, the most commonly used antibiotic susceptibility testing methods (i.e. antibiotic susceptibility testing; AST) rely on phenotypic detection (i.e. disk diffusion, microdilution, cultures etc.); methods which require analysis times ranging from hours to days. Electrochemical methods of AST that successfully meld electrochemical detection to biological processes is an emerging field; with the technology only beginning to become clinically relevant in the last 5-7 years. A rapid, point-of-care biosensor to identify drug susceptibility in patient samples will reduce health care costs and accelerate the treatment of bacterial infections as well as cancer. Based on a urine or blood sample, doctors will be able to rapidly assess which antibiotic or chemotherapeutic drugs will be most effective. This technology could be employed by primary care physicians, not require laboratory facilities and advance clinical treatment towards the prescription of evidence-based personalized drug regimens. 

If a system can accurately and cost-effectively provide results on which antibiotic is the most effective in < 2 hours, we believe our technology could supplant the currently employed systems.

Applications

Human and Veterinary Medicine: This method can be used to detect antibiotic and anti‐cancer drug resistance in patients. It could also be used as a platform for the design and development of novel pharmaceutical drug candidates that overcome drug resistance in bacteria and cancer.

Opportunity

Current proof‑of‑concept studies have been done. UM is seeking a partner to assist in further development and validation of the technology for various classes of antibiotics and chemotherapeutics.